Former "Saturday Night Live" stars Tina Fey and Amy Poehler have been friends for more than 20 years now, but it has been seven years since they last starred in a film together. December's "Sisters" reunites the comedians and, in the new issue of Entertainment Weekly, they discussed the joys of working together once again.

"Tina and I have a pact that every seven years we have to work on a project together or else the curse of a witch comes true and one of us suddenly ages," Poehler told Entertainment Weekly.

In the comedy "Sisters," written by longtime "Saturday Night Live" writer and producer Paula Pell, Fey plays former party girl Kate, and Poehler is her recently-divorced, ultra-responsible sister Maura, according to E! The siblings decide to throw one last huge house party after they learn their parents are going to sell their childhood home.

"It would have been more expected to see me in the role of Maura," said Fey, who also served as a producer for the flick. "I thought the fun would be watching Maura lose her mind, and Amy would be so good. She's funnier than I would ever be at that."

The duo first met when they were still green to the comedy scene at Chicago's ImprovOlympic, according to the Daily Mail.

"It just wouldn't make sense playing sisters with anyone else," said Poehler. "There's an ease that we have with each other. Neither Tina or I have sisters in real life. We are each other's chosen sister. Like most sisters, we've never dated the same guy and we're great in photo shoots and fittings because we know what will look good on one another."

"Sisters," also starring Maya Roudolph, Kate McKinnon, Rachel Dratch, Ike Barinholtz and Jon Leguizamo, arrives in theaters Dec. 18.