Brown began inking the Teenage Mutant Ninja Turtles in 1985 and continued until 1988 when he and partner Steve Lavigne began producing artwork for licensed TMNT products. Brown worked primarily as inker over Lavigne's pencils.
As a Mirage Studios staff artist Brown designed many Teenage Mutant Ninja Turtles action such as figure Farmer Mike for Playmates Toys. According to credits included on the back of Turtles action figures Brown also created Hothead, Scratch, Monty Moose, King Lionheart, Halfcourt, Wyrm, Scumbug, Leatherhead, Doctor El, Wingnut & Screwloose, Ray Fillet, Sandstorm, Mondo Gecko and Rock 'N Roll Mondo Gecko. Brown's comic book series, The Selected is populated with his old unused TMNT toy designs.
Brown created Ninja April O'Neil in a 1985 pin-up published in the fourth printing of Teenage Mutant Ninja Turtles #1. He would later bring his interpretation of the character to the Teenage Mutant Ninja Turtles Adventures title published by Archie comics.
Scratch and Farmer Mike are un-credited on the back of the toy packaging but Brown has confirmed at different convention appearances that he did create the cat burglar as well as designed Farmer Mike.
He also notes that the stool pigeon included with the Scratch figure was created by long-time friend Dan Berger who he would later hire to ink the Archie TMNT Adventures title.
In the late 1980s, Brown, with partner Stephen Murphy, revamped the Archie TMNT Adventures title for Mirage Studios. The team of Brown and Murphy created the Mighty Mutanimals as a spin-off of the Adventures title. Brown inked over 80 covers for the Archie TMNT Adventures title.
Brown was a participant in the drafting of the Creator's Bill of Rights.
Brown also created the ABC Saturday morning animated television series, Wild West C.O.W.-Boys of Moo Mesa and helped with development on its corresponding video game for the arcade by Konami. The game itself easily compared to Konami's own Western game Sunset Riders. Also, near the years of 2011-2013, word has been said that Brown was to create a comic book series that was to be "The Next Generation of the Mutanimals" also known as "The SELECTED"..
Brown appears in the 2014 documentary film, Turtle Power: Definitive History of the Teenage Mutant Ninja Turtles, from Paramount Pictures.