Jennifer Feels Guilty for 'Ellen' Prank on Justin

Jennifer Aniston's boyfriend and Wanderlust co-star Justin Theroux made his first appearance on The Ellen DeGeneres Show this afternoon, reluctantly showcasing his break dancing skills, and this Thursday, Jennifer herself will appear on Ellen to provide some backstory on just how she was able to set up her beau without him being any the wiser.

While she expressed remorse for helping to coordinate Justin's impromptu dance session, Aniston says she gave Theroux fair warning-- a warning he did not heed.

Justin Puts the Moves on Jen in Wanderlust

"I feel quite guilty about this," Jennifer told Ellen. "I said you should probably be prepared because Ellen likes to surprise with things. Like one time she made me sing and one time she gave me vibrating things…I don't know, you do games and stuff . He was like, 'she won't do that to me. I'm a first-time guest.' I was like, 'You're right. She would never do that to you honey.' And there I go and I help you in your trickery…"

Jennifer Aniston Receives Star on The Walk of Fame

Watch the clip for more, and don't miss Jennifer's full appearance tomorrow on The Ellen DeGeneres Show. Check your local listings.