Peter Laird and Kevin Eastman
Long story short: Eastman and Laird created the TMNT back in 1983 and debuted them the following year with a comic book of the same name. They were heavily involved in the series from 1984 to about 1989 when they become more involved in business management than comics. Most of the Eastman and Laird issues were basically graphic novellas, consisting of 40-50 pages and usually self-contained stories. These issues introduced the main characters and mythos plus many other characters, organizations and situations that were later made famous by the toys, cartoon, and movies, including: Shredder, the Foot Clan, Baxter Stockman, the Mousers, Casey Jones, Triceratons, and Fugitoid.
TMNT Book IV First Comics Collection cover by Eastman
TMNT #11 cover by Eastman
TMNT Guide to the Universe RPG book cover by Laird