The Knight Rider TV movie/pilot is going to air on NBC on February 17th, but Will Arnett won't be voicing KITT as originally announced. It turns out that since Will Arnett did voiceovers for some GMC trucks commercials, they were not too pleased with him creating a conflict of interest by voicing a competitor's (Ford's) vehicle. So now the Mustang is going to be voiced by Val Kilmer despite the fact that they had finished all work with Arnett. Though the announcement just became public, it's likely Kilmer was brought in a while ago.

I believe this is an accurate representation about how it all went down:

In case you're curious, here's one of the GMC truck commercials Arnett voiced:

Good thing I just recently created the Super Lame topic, it's highly appropriate for this story.