Will Arnett (Arrested Development) has had to give up his part as the voice of KITT in the upcoming NBC Knight Rider reboot due to some contractual difficulty he has with General Motors. See, Arnett has been a voiceover artist for GM for the better part of the past decade, and the cars used in Knight Rider will be Ford Automobiles. Not only will Ford be providing the automobiles for the show, they are taking an active role in the promotion of the show, as well, so naturally GM doesn't want their spokesman working on it.
So, the producers have had to scramble and find someone else to redo the already-completed voice of KITT, and they've scored a winner with the Real Genius himself, Val Kilmer. Kilmer will go in soon to record the voice, and he'd better hurry since the movie is scheduled to be aired on NBC in the next couple of weeks.
Variety.com: Val Kilmer voices 'Knight Rider'