The LOL-moment went down on Ellen DeGeneres' new show Repeat After Me. Bieber was told via hidden microphones to shake his thang on the random grandma, and let's just say, the whole situation made her super uncomfortable.
In his episode, the Biebs pretends to take private bowling lessons from the sweet, older-lady instructor, who doesn't know he's actually repeating everything host Wendi McLendon-Covey tells him to do and say via a remote earpiece.
"The Biebs only does hugs," he says to the teacher when she walks in the alley. He tells her he's making a movie called Bieber Be Ballin'.
"It's a documentary about how good I am about handling balls," he jokes, before he's told to "stay close" to the instructor and "hug her and don't let go."
Surprisingly, she handles that well until badass Justin asks her if she's ever robbed a liquor store. "No," she responds, moving away from him. "Why would I want to do that?"
That's when Justin's asked to twerk on her...and he does. Repeat After Me airs Tuesdays (8:30 p.m. ET) on ABC. Watch the Biebs' clip below.