If you tuned in to ''MTV's Spring Break,'' you saw more than tight bodies in bikinis. One of the hosts was Lindsay Lohan. Makes sense: Lohan stars in ''Mean Girls,'' a movie from MTV's corporate cousin, Paramount Pictures. But, these days, stars of the geeky high school comedy ''Napoleon Dynamite'' are popping up all over the cable channel too. Unlike most movies that get lots of MTV airtime, ''Dynamite'''s not a Paramount property. Fox Searchlight, which purchased distribution rights to the movie at Sundance, agreed to have MTV Films ''copresent'' the movie, tapping into MTV's young, free-spending audience. Apparently, that audience won't have to spend much. ''It doesn't need to make a whole lot of money to be very successful,'' says MTV Films' exec VP David Gale about the cheap indie. ''It's not 'Spider-Man 2.'''