Lawrence, as detective Malcolm Turner, is after a killer, and apparently the only way to capture him is to pose as the bad guy’s ex-girlfriend’s grandmother, who--the film cannot stress this point too much--is quite large.
Apparently, Sherry (Nia Long), the young woman in question--she’s as attractive as Big Momma is, well, you know--is none too bright, for she falls for Malcolm’s ruse, which of course ostensibly amuses mainly because it’s so transparent. She at least has an excuse--she hasn’t seen Big Momma in two years--but Big Momma’s oblivious friends are functional morons.
All I can say is that this was by far one of the funniest movies I have ever seen. I enjoyed it so much, that I went back to see the movie twice. Martin Lawrence was very, very funny. I laughed so hard that I was embarassing myself.