Micah Fowler explained on Twitter that his character, JJ Dimeo, has a more severe form of cerebral palsy than he does in real life. His character, JJ, is nonverbal and uses a power wheelchair for independence; Micah uses a wheelchair most of the time but can walk short distances with a walker, and he can talk clearly enough for most people to understand him.
Micah Fowler was cast purely on the basis of audition videos. He never met or spoke to the producers prior to being cast as JJ.
Each episode's title is written as J.J. spelling them out and whoever is reading what he is saying them. This usually happens multiple times in each episode. J.J. "T-y-p Types" what he wants to say.