People.com Entertainment Movies Aubrey Plaza Talks Filming Sex Scene with Robert De Niro for 'Dirty Grandpa' : 'A Lot of Interesting Stuff Went Down' Plaza also said she heard De Niro "was legitimately scared of me" By Jodi Guglielmi Jodi Guglielmi Instagram Twitter Writer-Reporter, PEOPLE People Editorial Guidelines Published on January 20, 2016 06:05 PM Share Tweet Pin Email The relationship between Aubrey Plaza and Robert De Niro in the upcoming film Dirty Grandpa is a true love story kind of. In the film, Plaza and De Niro play your typical love interests – except that she’s supposed to be 21 and he’s, well, a grandpa. “We’re soulmates,” joked Plaza, 31, on Jimmy Kimmel Live! Tuesday night. “Robert De Niro’s character lies and says he’s a professor and my character has this obsession with having sex with a professor so I kind of zero in on him.” “He’s met his match with me,” she continued. “He’s a dirty grandpa and I’m a dirty girl.” Plaza recalled filming a graphic sex scene with De Niro, 73, noting that it took “a solid nine, maybe ten” hours to complete – and the details are nothing short of hilarious. “There was a lot of interesting stuff that went down, you know,” she said. “We didn’t totally plan out the scene, so we didn’t really know what was going to go down.” During the all-day shoot, Plaza said the director would often pull her aside and give her instructions on what to try for each take. While some things worked, others definitely did not. “I’d try to get in there and suck on his nipples, and he was like batting me away, and I didn’t know if it was in character or not,” she said. “And then they’d cut the camera and [the director] called me back and was like ‘Bob does not like his nipple area paid attention to.’ “I was like, ‘Great, now he thinks that I wanted to do that,’ ” she laughed. “It was a lot of really fun moments.” While working with a veteran actor like De Niro seems intimidating, it turns out De Niro was the one nervous to work with Plaza. “I heard from my agent, who had spoken to his agent that he was legitimately scared of me,” she said. Plaza explained that she thought it might have been more about her “terrifying” sex-obsessed college coed character than her personally. “Every time I was around him it was right before we started shooting, so I would be all over him and I think I really freaked him out,” she said. Dirty Grandpa hits theaters Jan. 22.