Michelangelo is consistently portrayed as the most light-hearted and friendly of the four Turtle brothers. Upbeat and good-natured, 'Mikey' (an affectionate nickname frequently used by his brothers) prefers to spend his time enjoying his life. While his brothers wrestle with the implications of their mutation and their place in the world, Michelangelo enjoys relaxing in front of the TV, skateboarding throughout the labyrinthine underground sewers that the Turtles have made their home, reading comic books, and eating lots of pizza, of which Michelangelo's favorite is either pepperoni or anchovy. Michelangelo's innocent and childlike personality has led to him being referred to as the youngest brother. Due to being the youngest of the family, Michelangelo's brothers, especially Raphael, assume a protective watch over him whenever they venture outside of their abode, and they habitually expect little of their youngest sibling during serious discussions. In the 2007 movie, Michelangelo is referred to by Leonardo as 'Little Brother'.

Though his abilities are often underestimated due to his position in the band of brothers, throughout the series Michelangelo reveals an unparalleled level of sensitivity to the feelings of those around him and, as a result, feels a very real and serious need to help those he believes are less fortunate than he. Michelangelo despises confrontation and avoids fights (especially with his brothers) at almost all costs. He simply laughs off most insults thrown his way and prefers to take a more light-hearted approach to solving problems. The other Turtles frequently become frustrated with his constant tendency to downplay serious situations and joke around during them, and it is this attitude that causes most of the conflicts between Michelangelo and his brothers throughout the series. Because of Michelangelo's happy-go-lucky and goofball nature, he is often the main source of comic relief in the comics and shows, his brothers often serving as the (unwitting and unwilling) butt of his jokes.

Despite their personality differences, Michelangelo generally gets along well with his brothers. He admires Leonardo (also known among the brothers as 'Leo') for acting as the archetypal eldest brother and de facto leader, as well as a strict practitioner of bushido and ninjitsu. Michelangelo views Leonardo almost as a parental figure and will often look to him for reassurance. Leonardo is the stable pillar in Michelangelo's life, always silently watching and waiting, doing his best to ensure the safety of his younger brother. Leonardo frequently raises the issue of Michelangelo's safety in the 2007 film, on one occasion asking who would guard Michelangelo while he was gone. When they reunite later on, Leonardo is embarrassed when Michelangelo (who missed Leonardo as well) hugs him. In the 2003 animated series, when Michelangelo is challenged to a fight in the episode 'Grudge Match', Leonardo takes up the responsibility of being Michelangelo's trainer. When the time comes for the match, Leonardo reassures Michelangelo by saying that '...If one falls, we all fall.'

Similarly, Michelangelo looks to the hot-tempered and aggressive Raphael for emotional support and protection. Although Raphael acts tough and rebellious, he cares deeply for Michelangelo, even openly admitting that the mere thought of his youngest brother being grievously injured causes him to experience violent rage. Michelangelo knows that Raphael will do everything in his power to protect him. However, out of all his brothers, Michelangelo spends the most time with his genius brother, Donatello. Despite vastly different interests and personalities, the pair seem to get along very well and rely heavily upon one another when fights occur between Leonardo and Raphael. Their closeness probably stems from their passive personalities, which set them apart from the more authoritative Leonardo and confrontational Raphael, and makes them common sparring and video game partners.

Although a well-trained ninja, Michelangelo is primarily a social being and lacks the discipline of Leonardo, the relentless ferocity of Raphael, and the quick mind of Donatello. However, Michelangelo makes up for these losses with the boundless energy, unorthodox fighting style, and fierce determination that he shows when he fights alongside his brothers. In several portrayals, Michelangelo exhibits a strongly creative side. In a side story in volume 2 of Tales of the TMNT, it is revealed that at an early age, Michelangelo was a talented artist. In the Image comics, Michelangelo became a published author.

Throughout the various versions of the TMNT, Michelangelo has had romantic relationships, but all of his girlfriends have been aliens. The first, in the original cartoon, was the Neutrino girl, Kala; his second was Horridus ("Sara") in the Image comic series; and his third was an alien humanoid dinosaur princess (known as a "Regenta") named Seri, in Volume 4 of the comics. In the third TMNT movie, Michelangelo also has one-sided feelings for a woman named Mitsu, the leader of a group of rebels who were trying to overthrow Lord Norinaga. In fact he, Leonardo, and Raphael all expressed wishes to stay in the past with her (albeit all for different reasons). Michelangelo is also quite close to April O'Neil.

Mirage

In the original comic books, Michelangelo was initially depicted as fun-loving, carefree, and, while not as aggressive as Raphael, always ready to fight. He is much more serious-natured in the comic book than in the film incarnations, which have labeled his character a permanent "dude" talking pre-teen. It was Michelangelo's one-shot in this series that fleshed out most of the traits that have become synonymous with the character, such as his playfulness, empathy, and easygoing nature. In one-shot story, Michelangelo adopts a stray cat (which he names Klunk) and also stops thieves from stealing toys meant for orphaned children.

After their defeat at the hands of the Foot Clan the Turtles, Splinter, April O'Neil, and Casey Jones retreat to a farm house in Northampton, Massachusetts which used to belong to Casey's grandmother. While there, April is worried to note that Michelangelo is not himself. He spends his days in the barn taking out his aggression on a punching bag. A scene shows him lashing out at his surroundings and repeatedly punching the wall of the barn until it breaks, then collapsing on it despondently, anger spent. The end of the story implies that Michelangelo's sorrow and frustration have been resolved, as subsequent issues restore Michelangelo's more relaxed, optimistic personality.

It is during the group's time at the farm we learn that Michelangelo also has an interest in comic books, specifically ones involving superheroes such as "The Justice Force" (comic book heroes based on The Justice League and The Fantastic Four). He also finds solace in writing fiction and has produced a story depicting himself as a ronin in Feudal Japan.

In the issue "City at War", Michelangelo instantly bonds with Casey Jones' adopted daughter Shadow, who nicknames him "Rooish". In the second volume, the Turtles decide to try to live apart from one another. Michelangelo, social creature that he is, moves in with April and Casey so that he can be close to Shadow. Throughout the first two volumes, Michelangelo seemed to act as peacemaker of the team. These stories also laid the foundations which demonstrated his closeness with Donatello, their laid-back natures separating them from the more contentious Leonardo and Raphael.

In Volume 4, Michelangelo gets a job as a tour guide showing alien visitors around Earth. His first (and only) tourist is the Regenta (or "princess") Seri of the Styracodon race. Michelangelo convinces Seri to sneak away from her bodyguards so that he can take her on a tour of the northwest coast of the U.S. Unfortunately, his plan lands him in trouble when Seri's bodyguards become aware of his machinations. They attack Michelangelo and transport him back to their home world, were he is placed in prison. With the help of a Triceraton prisoner named Azokk, he manages to escape, and is rescued by a group of Triceratons who came to rescue Azokk.

Michelangelo was not given an especially large role in Volumes 1 and 2, did little to advance the plot, and was often not portrayed as an especially skilled fighter. His relatively small role was probably due to the need to establish Leonardo's role as "leader" along with the fact that Donatello was Peter Laird's favorite Turtle, and Raphael was Kevin Eastman's favorite.

Image

In the comics published by Image, Michelangelo's interest in writing is expanded upon and he is established as a writer of fiction and poetry. An early issue has him selling his first poem to a poetry digest. As the comic continued, Michelangelo's career as a writer gradually expanded. In the final issue, he has published his first novel, a romance called "A Rose Among the Thorns". April mentions that the book was already going back for a second printing and that she'd heard that Oprah Winfrey loved it, which "practically guarantees that it will be a best-seller". It is interesting to note that Michelangelo is the only Turtle who did not end up disfigured in some way in this series; Leonardo lost his left hand and had it replaced by a steel cap with a retractable blade, Raphael was facially disfigured after being shot in the face, and Donatello was transformed into a cyborg after being shot and thrown out of a helicopter.

Archie

In the Archie Comics series, Michelangelo was initially presented very similarly to his 1987 cartoon portrayal-understandable, considering that the comic started as an adaption of the popular animated series. As the series progressed, Archie's Michelangelo was presented as more mature than the cartoon version. This version developed also an interest in poetry. During a battle, he was temporarily blinded and later captured by the U.S. Military, whereupon he was interrogated and tortured. He was eventually rescued by his family and saved the life of the man who tortured him.

One of his many skills in the Archie comics was the ability to communicate with animals. In a storyline set in the future, Michelangelo is shown to have become an artist whose main job is running an orphanage.

Michelangelo's persona became strongly established in the 1987 animated series. He was often seen as a "Party Dude", which, though accurate in the 1987 series (which gave him this title in the theme song), accounts for only part of his personality otherwise. As the "party dude", he usually didn't have much input in the team's plans, although he was still just as active as his brothers. He typically spent much of his time joking and socializing with other characters. He is most associated with the "Cowabunga" expression that became a pop culture phenomenon.

Michelangelo had a fondness for pizza, even beyond that of the other Turtles; in the Season 3 episode Cowabunga, Shredhead, his pizza cravings annoyed the others so much that Splinter hypnotized him into refusing and denouncing pizza whenever the very word was mentioned, although the hypnosis was lifted at the end of the episode. He was essentially a provider of comic relief, despite Raphael taking the role as the joker and comic relief in this incarnation.

Michelangelo also received his distinctive voice, which has been imitated in other portrayals of him, in the 1990 series. Employing a "surfer slang" vocabulary, he customarily spoke with a unique hybrid of a Californian surfer accent (not unlike the speech of the Spicoli character from Fast Times at Ridgemont High) and what may have been a stereotypical "stoner" accent, though no reference is ever made to narcotics in the series. In fact, Michelangelo appeared in a 1992 animated special, Cartoon All-Stars to the Rescue, alongside other famous cartoon characters, intended to inform children about the dangers of substance abuse. Additionally, all four of the Turtles were official "spokes-turtles" of the "Just Say No" anti-drug campaign, despite accusations that at least one of them exhibited characteristics of a stoner. During one of these anti-drug PSAs, Michelangelo suggests to a kid being tempted with marijuana that he should "get a pizza" to go with it, before the idea is shot down by Donatello.

Michelangelo's trademark phrase in this series is the infamous "Cowabunga." In the original English language version of the 1987 series, Michelangelo's voice actor was Townsend Coleman, and in the 25th anniversary movie Turtles Forever, was voiced by Johnny Castro.

In the 2003 TV series, Michelangelo is voiced by Wayne Grayson. Known as 'Mikey' to his brothers, his personality is more akin to the Mirage comics than the 1987 show. Still the comic relief, he often makes statements that spoof pop culture, although he uses less surfer slang than in the 1987 cartoon. His trademark nunchaku are once again his primary weapons, but he has used other weapons such as grappling hooks and those of his brothers. He is slightly more immature than in the 1987 series-particularly apparent by a high-pitched scream. Unlike other incarnations, he was often more reluctant to fight and he likes to tease and annoy his older brothers, especially Raphael, for whom Michelangelo is the foil. In fact, a running gag is that whenever Michelangelo says or does something excessively outrageous and stupid, usually involving a catch-phrase from the 1987 show, one of his brothers (usually Raphael) will slap him on the head. Other characters such as Master Splinter and the Ancient One have picked up on this habit but usually whenever he disobeys. In the Fast Forward episode Time is Everything, when Michelangelo was talking too much, Splinter flipped over his seat he was sitting on causing him to fall on the ground, replying afterwards that "Somebody had to do it. It was...time."

Raphael and Michelangelo mostly have a love-hate relationship in which Michelangelo frequently antagonizes Raphael (it especially hurts Raphael's pride that Michelangelo has bested him more than once, both times because Raphael's anger got in the way), but Raphael shows that he cares about him whenever he's in danger. He also seems to be very close with Donatello. When Mikey was a kid, he and his brothers went with Master Splinter to Japan to bury Master Yoshi's ashes next to his beloved. While there they helped Master Splinter and the Ancient One win a fight against a ghost and that is when they gain their ninja masks. This happens in the episode (Fathers and Sons).

Michelangelo is regularly treated as the youngest brother and little is expected of him. However, he has shown innocent empathy for others as shown in particular by his adoption of Klunk the stray kitten, to whom he is very close and also by his relationship with Leatherhead. It is his initial awareness of Leatherhead's humanity which ends up forging the bond between the crocodile and the other Turtles. He enjoys Leatherhead's company, although he can tease him on occasion against his better judgment. However, he cares greatly for the crocodile and is quick and willing to forgive and reassure him when a rampaging Leatherhead injures him in a blind, nightmarish rage in the episode 'Hunted.' Leatherhead also appears to care greatly for Michelangelo and is distraught when he believes he has fatally injured him, but delighted to discover that his fears are unfounded when he finds out that the turtle is alive and well.

As in the Mirage comics, Michelangelo is an avid fan of comic book superheroes. In some episodes, he takes on the role of a costumed super hero called "Turtle Titan" and befriends other superheroes such as the "Silver Sentry" and the "Justice Force". As Turtle Titan, Michelangelo uses grappling hooks as both a weapon and a mode of transportation.

Although not shown as particularly focused on ninjutsu, preferring to spend his time reading comics or watching movies, he is quite an effective fighter and in the Season 2 finale, he became the Battle Nexus Champion, considered the best fighter in the multiverse. Although his victory was due in part to some very lucky breaks, Michelangelo later won a rematch against the last finalist and earned a medal of honor for his behavior during the battle.

In the crossover movie, Turtles Forever, Mikey is the only Turtle who initially likes their comedic 1987 counterparts (he is especially fascinated by the initials on their belt buckles). However, he eventually gets tired of their laid-back attitudes and yells at them when they don't take the 2003 incarnation of Shredder seriously, proving even this version of Mikey has his limits to fooling around.

In early profiles of the 2003 animated series, Michelangelo is regarded as being the most athletic of the four, although unfocused on training mentally (though those are admittedly old profiles and may have been early plans for the character, he has certainly proven he is an effective fighter when need be). This profile statement has since been repeated in the profile of Michelangelo in the lead-up to the debut of the Fast Forward season which began airing on July 29, 2006.

Michelangelo is depicted in the live-action movies as the easy-going, free-spirited turtle. One of his movie catch phrases is, "I love being a turtle!" Owing to his popularity with children, he is given many lines and comes up with several (slightly outrageous) plans to advance plots. In the first movie, he and Donatello were regularly paired together while Leonardo and Raphael were arguing. In the first movie and the first sequel, The Secret of the Ooze, he was portrayed by Michelan Sisti; in the second sequel, Teenage Mutant Ninja Turtles III, he was portrayed by David Fraser. In all three movies, he was voiced by Robbie Rist.

In the 2007 TMNT film, Mikey has taken to performing at children's birthday parties as "Cowabunga Carl" in order to help make ends meet to support his family. It becomes apparent early in the film that the physical and emotional absence of his older brothers has finally begun to affect the outgoing Michelangelo. Unlike his other incarnations, the 2007 Mikey seems to draw the most emotional support from Donatello instead of his oldest brothers, Leonardo and Raphael.

Upon Leonardo's return from Central America, Mikey gives his oldest brother an enthusiastic hug, falling over the couch and tripping over furniture in his excitement. Mikey's lively and innocent demeanor returns in full force when he is in the protective presence of his three brothers again, his good-natured jokes and brief commentaries lightening even in hard situations. Clearly, despite the hardship that his family has recently experienced, Michelangelo has retained much of his usual goofy, laid-back personality and still remains the main form of funny. He is voiced by Mikey Kelley.

When looking at all four brothers in the 2007 movie, one notices that Michelangelo has blue eyes where the other three have brown. This cuts continuity since in all other film incarnations, Mikey has brown eyes. According to the film's director, this was done to make Michelangelo seem a bit more innocent and younger than the other turtles. He is a fantastic skateboarder in this movie, able to complete many tricks underground.

In the video games based on the 1990 animated series, Michelangelo is usually the slowest but strongest of the Turtles. However, to reflect his flashy personality, this trend was reversed and he became the fastest Turtle in the video games based on the 2003 animated series; Raphael became the strongest. Michelangelo appears in Smash Up as a playable character, and is voiced by Wayne Grayson.

The character's name was originally misspelled as "Michaelangelo", with an additional "a". This misspelling had stuck until 2001 with Volume 4 of the comic series from Mirage Studios, when the spelling was officially changed to "Michelangelo". The 1996 anime also used the "Michelangelo" spelling. On the TMNT 2007 movie teaser poster featuring Michelangelo, we see the "Michaelangelo" spelling, though the movie uses the proper spelling of the name in its credits.

Klunk

Klunk is Michelangelo's pet cat. He first appeared in the Michelangelo microseries, and was hit by a car and died in the Tales of the TMNT vol. 2 issue 9. Shortly after, the Turtles discovered that Klunk had mated and had kittens with an alley cat.

Klunk also appears in a few episodes of the 2003 cartoon, starting with The Christmas Aliens. Based on the revamped character designs in the Back to the Sewers season, this version of Klunk appears to be female, whereas the Klunk from the Mirage comic was confirmed to be male.