Fallon also teaches WWE Superstar a dance move for his wedding he learned from Madonna.
The Nickelodeon Kids' Choice Awards host played Addison, a teenage girl who's had "a little bit of a growth spurt" since last seeing her friend Sara (Fallon) three years ago.
"The football team is all, like, trying to recruit me and stuff, and they're, like, 'Why don't you throw things?' And I'm like, 'Ew, throwing things,' but now I totally love it, watch this," Cena says before tossing a pillow at a vase and smashing it to pieces.
The moment, though scripted, was too much for Cena to handle and he couldn't resist laughing himself. He also lost it when it came time to practice dance team auditions to Bruno Mars' "Finesse," laughing hysterically when he picked up Fallon for a twirl.
We can't blame him for breaking character though, that sketch looks like pure joy to participate in.
There was more dancing on the "Tonight Show" set during the interview portion of Cena's appearance. Fallon taught the WWE star Madonna's "girls gone wild" dance move, which he can whip out to impress his fiancé Nikki Bella at their upcoming wedding.
Watch that video below: