Zac Efron's Bad Neighbours 2 co-star Beanie Feldstein has recalled an "awkward situation" when the handsome actor accidentally copped a feel.

Bad Neighbours 2 sees the return of couple Mac Radner (Seth Rogen) and pregnant wife Kelly (Rose Byrne), who are enjoying life in the suburbs as new parents until a group of unruly sorority sisters move in next door, one of which is played by Beanie. As the loud parties threaten the sale of their home, the couple turn to ex-neighbour and one-time enemy Teddy Sanders (Zac Efron) for help.

During an appearance on TBS' late night show Conan, Beanie shared an amusing tale involving Zac, who was in attendance at a press conference to promote the new movie.

Beanie recalled to host Conan O'Brien how Zac, 28, was in charge of filming short videos of the junket to be posted on social media app Snapchat and at one point went over to the stage were Beanie and her colleagues were sitting.

"So he comes over and interrupts our interview and gives us all hugs, but we're sitting down, me and the other sorority girls, Kiersey (Clemons) and Chloe (Grace Moretz), so he gives us hugs from behind and then he disappears into the night like the stallion that he is and we don't see him for the rest of the day," she explained, causing the audience to burst into laughter.

"The next day he comes up to me, and he's like, 'I'm so sorry,' and I was like 'Hey Zac, what's going on?' And he was like 'I was re-watching the Snapchat and I think I touched your boob. I'm so sorry.'"

Even though Beanie, the younger sister of actor Jonah Hill, noted that Zac was clearly "horrified" by the incident, she was more upset that she had been oblivious to what had happened.

"In my head I'm like, 'OK Zac Efron touched my boob and I missed it! No, That's not fair!'" she laughed.

Bad Neighbours 2 is now showing in cinemas.