Most famous as the co-creator of the Teenage Mutant Ninja Turtles comic books, this cartoonist and author also published a comic book called Stupid Heroes and co-wrote a graphic novel series titled Planet Racers.
Early in his career, he worked as an illustrator for a Northampton, Massachusetts newspaper and provided artwork for a magazine called The Oracle.
He established a nonprofit artistic grant organization called the Xeric Foundation.
He and his brother Don grew up in North Adams, Massachusetts.
He and Kevin Eastman co-wrote the Teenage Mutant Ninja Turtles comics.