Tommy Mole

I have a 2 year old son who loves to read.  In our yard there were some mole tunnels that I pointed out to him.  He started to say things like "Tommy Mole was here" and still does whenever we are in that area of our yard.  Tommy Mole is something he came up with, but for some reason it sounds familiar to me.  I think maybe it was a character in a book we've read, but I have no idea which one.  Does anyone else out there have any ideas!