Get this: A soon-to-be groom attends a bachelor party, wakes up the next morning only to find one of the stripper/dancers from his party in bed with him, and later discovers the dancer really is the cousin of his future bride.

This is the rather weak premise of “A Guy Thing,” a romantic comedy directed by Chris Koch (“Snow Day”). The film rather obliquely, and unsuccessfully, attempts to ex-plain the man’s role in relating to women.

Jason Lee plays the hapless groom Paul and Selma Blair plays Karen, his slightly uptight – and rich – fiancee. Julia Stiles gives a decent comedic performance as Karen’s klutzy and fun cousin Becky, but unfortunately Becky’s role is about as shallow as a puddle.

In all, the funniest performances come from peripheral characters such as Paul’s minister neighbor (Larry Miller) who finds his son with some of Paul’s incriminating photos, and ends up officiating at Paul and Karen’s wedding.

Since a plot in which a groom tries to keep his bride and her family from discovering his supposed indiscretions only can sustain a movie for so long, Becky’s enraged ex-boyfriend cop shows up to terrorize Paul. Sigh.

The screenplay, by Glenn Glienna, is less than original. Perhaps that stems from Glienna’s having written a draft of “Meet the Parents,” a similar, but funnier, film.

As for the acting, it could have been better. Blair plays her character in a manner more boring than a CNN broadcast. She does have the “I think something is up but I’m not sure what it is and I’m not happy about it” pout down pat. Too bad she uses that pout a little too often.

As mentioned earlier, Stiles was fun to watch, but the film does not explain her motivations for almost all her actions. Lee has good comic timing, but he wasn’t given too much to work with.

“A Guy Thing” does deliver some great laughs, notably when a pharmacy worker caters a meal and slips marijuana in the food. Watching the guests, especially the usually straight-laced parents of the bride, get high is pure hilarity.

Some laughs fall flat. Gross humor substitutes for irony in some cases. A little too much groin-itching goes on, and Paul pretends to have diarrhea by squeezing a bottle of shampoo into the toilet.

The most fun comes from watching the men in the movie being chauvinistic and stupid, but these laughs come cheap.

The end result: It could’ve been better.