Look who's still, well, "Friends."

In a new promo for today's episode of "Ellen," Jennifer Aniston, who will co-host the talk show for a day, needs advice and a few "dumb jokes." So, naturally, she decides to visit the home of her former "Friends" co-star Matthew Perry, who seems very confused by her visit.

"What? What are you talking about? We used to walk into each others' apartments all the time," she says, when he asks her to call before showing up next time. "We're friends!"

"That was a TV show," he responds. "We actually haven't seen each other in a really long time. Like, eight years!"

After calling Perry "David" (a reference to David Schwimmer, who played Ross on the NBC sitcom), the mistaken identities continue when Courteney Cox appears from inside the house, and shrieks, "Lisa [Kudrow]?"

"It's Jennifer!" Aniston replies.

To find out how Justin Theroux factors into the conversation, and what two other very famous women sneak out of Perry's house, watch the video above.