There's Something About Mary (1998)

Ted Stroehmann (Ben Stiller) still finds himself thinking about his old crush Mary (Cameron Diaz) years and years after their disastrous and only date. Convinced that she still may be the girl for him, he hires private investigator Pat Healy (Matt Dillon) to track her down—but Healy himself falls for Mary, and secretly goes to lengths Ted could never imagine to win her over. When Ted eventually makes the trek south to visit Mary, he finds out that he’s got competition—and from more than one suitor. Only by being his own sweet self can Ted prove to Mary that he’s been the one for her all along.