Friends forever!

Jennifer Aniston and Justin Theroux celebrated their pal Ben Stiller's Saturday Night Live hosting gig at the afterparty. A source tells Us Weekly Aniston, 42, and Theroux, 40, arrived to NYC's Primehouse around 1 a.m. Sunday morning. 

VIDEO: Ben Stiller gets Jen Aniston "Naked" in hilarious PSA

"They were both wearing black," a source tells Us of the couple. "Justin was the complete gentleman." 

They sat in a booth with SNL castmembers Andy Samberg and Bill Hader. A source told Us they had "a variety of plates sent to them" during their 45 minutes at the table. "They grabbed a few drinks, [and] Jen ordered a Grey Goose on the rocks!" 

PHOTOS: Jen's romantic history

Last month, Theroux and Aniston went on a double date with Stiller and wife Christine Taylor at Il Cantinori in NYC. "Jennifer and Justin were really cute together -- affectionate but not over the top," a restaurant source told Us. "They seemed to be having a lot of fun with Ben and his wife, like old friends."

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