According to Dan Lebatard's interview with the Farrelly brothers today, Martin Lawrence was the studio's first choice to play the Ben Stiller character in There's Something About Mary, but he turned down the part. Daaaammmmn.
Weirdly enough, the minute Martin Lawrence destroyed his TV show and nearly killed himself, these interracial buddies movies just exploded. With Tucker wigging out, Murphy getting A-List Disney work and Chris Rock a better comedian than actor, Lawrence just rode a damn wave and was probably making $5 - $10 mil per script. Having those kinds of options and being a bit of douche to begin with, I can see him passing on something that self-deprecating. Also, I hate to say it, but I don't think a black protagonist would translate well, with that content, to the same audience.
just imaging martin lawrence playing the scene where he gets his stuff caught in the zipper makes me rofl