Dr. Tyler Rockwell is a character who appears in the 2012 TV series. He is a mutant monkey who was originally a human scientist. He first appears in the episode Monkey Brains.
When Dr. Victor Falco reported Rockwell missing on the news, Donatello and April investigate his disappearance hoping to find clues about the Kraang. While in his abandoned lab, they encounter Dr. Falco, who tells them that Rockwell had been using mutagen to experiment on monkeys. Donatello also takes a flash drive from the lab containing data on Rockwell's research.
The mutant monkey confronts them later. He attacks and defeats Donatello easily, and is about to harm April but calms down when she talks to him and runs away. April and the Turtles later search the city for the mutant monkey. Once they capture him, April realizes that the monkey is Dr. Rockwell. They return him to Falco, who promises to take care of him. But later, while studying Rockwell's flash, Donatello learns that Falco has lied to them about Rockwell.
The Turtles return to the lab just after Falco injects the psychic neuro-chemical from Rockwell's brain into his own. Falco defeats all the Turtles easily, but Donatello ultimately wins. The Turtles set the mutant Rockwell free, and he goes in the street. Despite hearing him get into a fight with an angry driver almost immediately, the Turtles decide Rockwell will be fine on his own.