Tim Allen's GalaxyQuest has an in-character audio track by the aliens....

These commentaries are hilarious.

Another one: Adam Sandler's Eight Crazy Nights...one commentary track is Whitey and Eleanore and one of the writers. I only heard about 5 minutes or so of it...interesting to hear Sandler start swearing in those voices...but just couldn't tolerate the voices in general...

How about Carrot Top's commentary for Rules of Attraction? No, he's not actually in the movie...but nonetheless...he's such a character! Sigh...that wasn't funny...but his commentary for that flick is pretty funny..."Hey Eric Stoltz...my brother! How about hooking me up with a movie role?"

Martin Landau is in character for the introduction of the Ed Wood commentary.

Actually, the Galaxy Quest is not a commentary track per se. It is billed as a Thermian Dialogue track - the intent was that the dialogue was 'dubbed' in the alien thermian language...

Ice Age has a "Movie Overview" commentary by Sid the Sloth (John Leguizamo) that's pretty good.

Mojo Jojo's commentary on "Slumbering With The Enemy" is a riot! "Go Mojesha, it's yo' birfday!"

In the Fairly Oddparents Movie, at one point Cosmo laughs and points out that Timmy's dad turns the video camera off when Mom is in the scene!

Fubar rules and so does the in character commentary.

I actually came here to ask this question again, nearly forgetting that's what I did last time I posted. I thought I thought about doing it, but never did it. Errr, hmmm.

Thanks for the replies. The Simpsons just BEGS for something like this. I hope they do it on at least one episode by the time all the DVD's are out.

On the Family Guy commentaries, Seth McFarlane and the voice actors occasionally slip into character to make comments on the show.

Same with the Futurama commentaries. John Di Maggio and Billy West often go into Bender and Fry voices (and the rest). Billy tries to go all out on one of them as Fry, not knowing who Billy West is.