Courteney Cox celebrated her Friends co-star Jennifer Aniston’s 51st birthday on Tuesday by posting this snap on Instagram of the pair looking very much alike:

“No matter how hard you might try… there’s only one Jennifer Aniston,” Courteney (aka Monica Geller in the hit sitcom) captioned the picture that Jennifer (who played Rachel Green) clearly enjoyed seeing on her feed:

Jennifer, meanwhile, marked her special day with an Instagram post thanking Interview magazine for using photographs of her on its front page.

“I had no idea this would be coming out today. Feeling proud and honoured to be celebrating with this cover,” Jennifer wrote. “Thanks to the Interview team for celebrating women at every age… turns out 51 is pretty fun.”

Other Friends stars also wished Jennifer a happy birthday on Instagram.

Lisa Kudrow, who played Phoebe Buffay, described her as “always beautiful and keeps getting more beautiful.”

And Matthew Perry (Chandler Bing) dedicated his fourth-ever post on the picture-sharing network that he only joined last week to the actor: