In the pic, Cox and Aniston, who co-starred together on Friends from 1994 to 2004, are sporting matching glasses. Cox also donned a wig for the shot, expertly matching her look to her pal's.
"No matter how hard you might try... there’s only one Jennifer Aniston," Cox captioned the photo. "Happy birthday my dear friend @jenniferaniston! I love you!♥️♥️♥️"
Reese Witherspoon, Aniston's Morning Show co-star, also celebrated the actress on social media, sharing a snap of them happily posing at an event.
"Happy Birthday Jen! 🌟," Witherspoon wrote. "I couldn't ask for a better friend and partner to chase my dreams with. Life is way more fun with you in it!!! 💯❣️"
Over on Twitter, Ellen DeGeneres joked about how she planned to celebrate her friend's birthday. "Happy birthday, Jennifer Aniston. I can't wait for our slumber party tonight. Portia bought Mad Libs!" DeGeneres quipped.
Happy birthday, Jennifer Aniston. I can't wait for our slumber party tonight. Portia bought Mad Libs!— Ellen DeGeneres (@TheEllenShow) February 11, 2020
In a sit-down with Sandra Bullock for Interview magazine, which dropped on her birthday, Aniston described how she envisions her life in the future.
"It’s not so much what I see myself doing, but it’s more like a little screenshot in my brain, where I hear the ocean, I see the ocean, I hear laughter, I see kids running, I hear ice in a glass, I smell food being cooked," she said. "That’s the joyous snapshot in my head."
Watch the video below for more on Aniston.