Grindhouse's trailers were done to keep in tone of the "Grindhouse" feel of the movie. Tropic Thunder's were done to establish the characters and the absurdity of Hollywood.
Big differences between the two.
Yes, I'm quite aware of the point, thank you. You're right, though, that there was a big difference between the fake trailers in Grindhouse
and those in Tropic Thunder
: the ones in Grindhouse
were actually interesting, whereas the ones in Tropic Thunder
merely made me wish the movie proper would hurry up and start. I would've much preferred more media coverage, interviews, etc., of the actors in order to establish the characters, instead of the yawn-inducing trailers.
I thought the trailers worked for establishing the characters. They give a laugh, they "throw you off" by just going right into them without any opening credits or even (IIRC) the movie's own studio animatics. I got a laugh out of all of them, not so much the energy drink one, but Black's mockery of the absurdness of The Nutty Professor movies, post-apoclyptic action movies with Stiller and I'm still laughing at the one with Tobey.
I think it "established" things well. Especially for the "movie within a movie" angle of things.