(CNN) -- Taylor Swift and Zac Efron are not a couple -- they repeat: they're not a couple -- but just because they don't have romantic feelings for one another doesn't mean they haven't spent some quality time.

As the two "The Lorax" co-stars revealed on "Ellen" Tuesday, Efron has picked up a few guitar-playing skills from Grammy-winning country star Swift.

"I got my first guitar lesson from Taylor," Efron told Ellen DeGeneres as Swift interjected, "He's really good at it, from like, one lesson. I taught him how to play 'Pumped Up Kicks' by Foster the People."

DeGeneres teased Swift, 22, and Efron, 24, throughout their time on her show that they acted awfully cozy, but Swift swears there's nothing going on between the two.

"We are not a couple," Swift emphasized. "He's awesome -- we're not a couple, though. You hear [about] people getting together when they're shooting movies, but not animated movie co-stars."

Her proof? While Efron had plans on Feb. 14 -- a screening, and then he cooked dinner "with a friend" who remained nameless -- Swift was hosting a "pathetic single girls party."

She invited all her single friends over to "eat junk food, and we ate whatever we wanted, and we danced, and we made these little profile cards about why we're single."

She explained of the concept, "That's actually what it was called, I'm not saying that being single is pathetic -- we've talked about this, and I think it's awesome."