Anna Faris is a giddy, carbonated blonde who gives the impression that her go-to cocktail is Cold Duck laced with Red Bull. She will do anything for a laugh, and does, in What's Your Number? Faris is endearing even at those times when this frantic I've-slept-with- 19-guys comedy is barely endurable.

Since this is a movie starring a woman who is not Julia Roberts or Meryl Streep, it follows that it is about a single girl desperate for a mate. Her name is Ally. Complicating her desperation is feeling that she is unworthy of love because she has had too many sexual encounters.

How many is too many? For Ally's mother (Blythe Danner), that would be 1. For her sister (Ari Graynor), that would be 4. For the magazine she consults as if it were Gospel, that would be 20. Women who have had 20 or more close encounters, says the magazine, are unlikely to find a lasting partner.

Ally's number is ... 19.

So that she does not hit or exceed the official "slut number," Ally sets out to find which of her exes might be recycled. This, during the run-up to her sister's wedding. Did the screenwriters order up a double shot of Ghosts of Boyfriends Past with a 27 Dresses chaser?

Ally's accomplice in tracking down her former beaux is Colin (Chris Evans, of Captain America renown), the player who lives across the hall and seeks refuge in Ally's flat as the hookup from the previous night vacates his premises.

Even for farce, the film's premise is pretty contrived. Plus, it's garish and so overlit that in scenes the actors resemble Madame Tussauds waxworks.

But the thing about Faris, the humor-seeking missile in Scary Movie, The House Bunny, and Lost in Translation, is that she is brazen in her pursuit of the laugh. Dance like a demented dervish, fall flat on her face drunk, lie like Pinocchio - this womanchild with the face of Goldie Hawn and the comic neurological system of Jerry Lewis gives it 200 percent.

In some scenes, Faris' sheer velocity gives the movie liftoff. In others, it doesn't hurt that Evans, who looks like the very young Alec Baldwin, and has the sonorous voice of Mark Feuerstein, is the film's sex object. Even someone not ordinarily an advocate of sexual objectification can make an exception in his case.

Contact movie critic Carrie Rickey at 215-854-5402 or crickey@phillynews.com. Read her blog, "Flickgrrl," at http://www.philly.com/flickgrrl/