Baseball is a game of legendary superstitions, jinxes and all manner of luck. The makers of “Fever Pitch” must have done something to please the baseball gods, because this movie enjoyed some of the greatest serendipity in film history when it was shot last summer.

“Fever Pitch” is a love story, set in the summer of 2004, about a diehard Boston Red Sox fan. Now, the filmmakers could not have known that the perennially heartbreaking Sox would win the World Series last year for the first time since 1918, after winning the pennant in an unprecedented comeback over the hated New York Yankees.

But the Sox did it, and this romantic comedy got a boost of pixie dust too cornball to believe, except that it really happened. (The script was hastily re-written to accommodate the twist.)

That’s part of the delight of “Fever Pitch,” but this film would have been a winner even if the Bosox had done their annual September swoon. It’s a dear picture that coasts nicely on the casually ingratiating appeal of its stars.

“Saturday Night Live” breakout boy Jimmy Fallon plays Ben, a Boston high-school teacher and full-time manchild. His life is defined by his season tickets to Fenway Park, willed to him by the beloved uncle who introduced him to the game.

Drew Barrymore is Lindsey, a business consultant who falls for Ben’s low-key charm. But as the season goes on, Lindsey’s patience is tested by Ben’s emotional commitment to his obsession.

One of the nice things about the movie is that these are two likable, good people who fall for each other quickly. There’s no dumb contrivances to keep them apart, no evil supporting characters we can hiss. Unless, that is, you think the baseball thing is a contrivance, in which case you’re probably not at this movie.

The script, by comedy vets Lowell Ganz and Babaloo Mandel, is adapted from Nick Hornby’s novel about a soccer fanatic. Leaving their indelible stamp are directors Peter and Bobby Farrelly, whose idea of a great first date is Lindsey’s bout of food poisoning and Ben cheerfully cleaning up her bathroom.

Publicity for the film is pushing the idea that “Fever Pitch” is a change-up for the Farrellys, who are known for the outrageousness of “Dumb and Dumber” and “Stuck on You.” But this is nonsense; they’ve always been sweet-natured and romantic – well, on their own terms, in between the bodily function jokes.

They’ve got Barrymore and Fallon almost too relaxed in their roles, but the laid-back approach works. Of course Lindsey is another Farrelly dream girl: She makes fun of women who whine about relationships, and quickly takes to baseball. (Recall Cameron Diaz in “There’s Something About Mary,” and her fondness for watching ESPN. Thank you for that fantasy, Farrellys.)

The jokes don’t always land, and it would be nice to have some strong supporting characters. Still, this is a pleasant night at the multiplex – and for baseball fans, the 2004 playoffs provide an unbeatable climax.