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In honor of Cox turning 57 on Tuesday, Aniston, 52, shared two tributes to her beloved friend on Instagram Stories.
Set to 50 Cent's "In Da Club," the first post featured a throwback video of Aniston and Cox holding hands - an image that then transitioned into a clip of the pair at the recent Friends reunion special on HBO Max.
"Happy Birthday to this ridiculously special human @courteneycoxofficial," Aniston wrote in the caption. "Time flies when you're having fun!"
For her second post, Aniston shared a photo of herself with Cox and the star's two dogs, Harley and Hopper.
"Who loves ya baby," The Morning Show actress captioned the group selfie.
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The sweet messages come just two days after Aniston celebrated the 17th birthday of Cox's daughter, Coco Arquette.
On her Instagram Stories, Aniston - who is Coco's godmother - posted several throwback photos of the teen while revealing the cute nickname she has for the birthday girl.
"Happy Birthday my sweet Cocolicious! Godmama LOVES you," she wrote at the time.
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Aniston and Cox have maintained a close relationship years after the end of their long-running series Friends.
In addition to appearing in Friends: The Reunion together, the pair recently sat down with their former castmates Lisa Kudrow, Matt LeBlanc, Matthew Perry, and David Schwimmer to speak to PEOPLE about their time together on the popular NBC series, which ran for 10 seasons from 1994 to 2004.
"It's still, to me, one of the greatest jobs I've ever had," Aniston said. "It goes so beyond the work and what the show was, which was, in and of itself, just a spectacular phenomenon, but the friendships and family that came out of it is just - you can't put words to that really. It's priceless."
Added Kudrow, 57: "And I know that I can text or call, and I feel like we can pick up right where we left off, and no time's passed. We're connected no matter what."