-> ''"Okay, I'm not going to sleep with one more guy until I'm sure he's the one. I may not have control over much, but I do have control over my pelvic floor. The next guy who vacations at [[UnusualEuphemism Casa Esperanza]] is going to be my husband!"''
A 2011 [[RomanticComedy rom com]] about [[Creator/AnnaFaris Ally Darling]], who, after yet another sexual partner that didn't want anything 'serious', comes across an article in a women's magazine saying that the average number of sexual partners women have had is 10.5, and women who sleep with over 20 men never find a husband. Her number? [[ReallyGetsAround 19!]] Actually, wait, make that 20.
Suddenly desperate, Ally and her [[TheCasanova playboy neighbor]] [[Creator/ChrisEvans Colin]] begin their search to find one of the 20 who may be "The One", so she can make him her husband without reaching the dreaded 21.
[[TheFilmOfTheBook Based on the novel]] ''20 Times A Lady'' by Karyn Bosnak, which was later re-released with the title 'What's Your Number' to match the film.
!!Tropes employed by this series are:
* [[TheLonelyIsland Andy Samberg]]: Plays Ally's [[spoiler: number one]] ex, Gerry Perry, AKA 'Creepy Puppet Guy'.
* TheBigBoard: ZigZagged. It's played for laughs when Colin makes one as part of tracking down Ally's ex, but somewhat straighter when he reveals that he learned how to make one from his dad the cop.
* ConcertClimax: A variant. Ally interrupts a band performing at a wedding in order to declare her love for the lead singer, [[spoiler: Colin]]. She is able to sneak on stage by pretending to be another band member and banging a tambourine.
* DeadpanSnarker: Colin, at times.
* FoolishSiblingResponsibleSibling: Ally and Daisy, respectively.
* HandsomeLech: Colin. He picks up his newspaper with just a ModestyBedsheet and hides out in Ally's apartment to avoid one of his one night stands.
* InnocentSwearing: Ally shouts 'fuck' in front of a group of children, who then repeat the word in confusion. A scene or two later, they're seen running around and shouting 'fuckitty-fuck!'
* KissingCousins: Ally's step-cousin Bo is on her 'People I've Slept With' list.
* [[LikeFatherLikeSon Like Father, Like Daughter]]: Ally's dad says she's more like him than her mother.
--> "You may have her looks, but you've got my rhythm, kid. And I'm afraid it's a little offbeat."
* MorningRoutine: Whenever Ally wakes up with a man she likes in her bed, she sneaks into the bathroom to brush her hair, put on mascara, and put a little toothpaste on her tongue before getting back into bed and pretending to have just woken up, so her partner won't think she's ugly in the morning.
* ReallyGetsAround: Ally, once she reads a magazine article about the typical number of partners and realizes she's way past that mark.
* RuleOfThree: Ally runs into her ex Donald three times, to his dismay.
* RunningGag: See RuleOfThree.
* SceneryCensor: Colin. Among other things, a bannister and a guitar.
* ShirtlessScene: Colin gets plenty of these, though he and Ally share one when they play [[StripPoker strip Horse]], not too surprising since it is Chris Evans.
* SkinnyDipping: Colin and Ally do this in the Boston Harbor. Then they realize it was a stupid idea because the water is ''cold''.
* WakeUpMakeUp: Parodied. See MorningRoutine above.
* WeddingDay: The last 20 minutes of the film takes place at Ally's sister Daisy's wedding, as well as numerous other weddings throughout Boston.
* WhatDidIDoLastNight: Ally wakes up from a night of heavy drinking and partying to find, to her horror, her ex-boss pantsless in her bed, effectively making him her number 20. [[spoiler: He's not because one of her past encounters calls her back and reveals that they didn't do anything because they were too drunk, so her ex-boss is #19 and Colin is actually #20.]]