Catch Phrase: In-universe example, Adam's Dad was once the star of a fictional comedy show called Great Scott. Thus everywhere he went, everyone asks him to say "Great Scott!" for them.
Defrosting Ice Queen: Emma is vehement in being cold and distant to Adam, but the more time she spends with him, the more she realizes that isn't who she wants to be all the time.
Dueling Movies: Friends with Benefits runs an incredibly similar plot to this film as you might have guessed, releasing six months after this one. And for an added bonus, the female lead of that movie is Natalie Portman's Black Swan co-star, Mila Kunis, who also played Aston Kutcher's girlfriend on That '70s Show (and following Kutcher's divorce, he and Kunis would date in real life). The male lead, Justin Timberlake used to be in *NSYNC, which once released an album called No Strings Attached.
Gold Digger: Vanessa, after she and Adam broke up. She cheated on him with his dad and told him straight up that she wanted to marry, have a baby and thus become Adam's stepmom. Thankfully, this plan was adverted at the end of the film.
Mood Whiplash: A big one when Adam confesses that he loves Emma and she responds by repeatedly punching him in full view of public. A police officer has to come by and break them up.
Naked First Impression: Adam, after a day of drinking away his sorrows he finds himself on the couch where Emma and her three friends stay at with only a hand towel over his area. Even better, according to Emma, he threw off all his clothes and danced around, waving his penis around the night before.
Nice Character, Mean Actor: In-universe and played straight. Everyone loves Alvin, but in real life, he treats his son Adam like crap like dating his ex-girlfriend Vanessa.
Sesquipedalian Loquaciousness: Emma and her fellow hospital coworkers/friends use these in quite a few jokes. Anytime Adam tries the same thing for them, they always accuse him of looking it up to which he humbly acknowledges so.
Sex Montage: Watch Ashton Kutcher and Natalie Portman merrily get it on all over the place with background music!
A Threesome Is Hot: Zigzagged. Initially two girls fall in love sitting on either side of Adam, and he just looks like he's caught in their moment. Then he takes them back to his place but when he goes in for a kiss one of them pushes him away. All of this only to serves to reinforce Emma's jealousy of course and leads to a Crowning Moment of Funny as she drunkenly kicks them out of his house.