Reese Witherspoon Calls 'Morning Show' Costar Jennifer Aniston 'Such a Gift' in Birthday Tribute

In addition to costarring in The Morning Show, Reese Witherspoon and Jennifer Aniston played sisters on Friends

Reese Witherspoon is honoring her friend Jennifer Aniston.

The Morning Show actress wished a happy birthday to her costar, 53, on Friday with a sweet birthday tribute. Alongside a photo of them on set, Witherspoon, 45, shared what she loves about Aniston.

"When I think of Jen and all the wonderful adventures we have had together, I just smile," Witherspoon wrote. "Knowing that @JenniferAniston is in the world makes me happy! Her love of life, her humor, and her endless positivity are such a gift. Let's all wish Jen Happy Birthday! 🎈🎂🎁."

While they currently appear on the Apple TV+ news drama together, Witherspoon and Aniston's work history goes way back. Witherspoon was a guest star on Friends and played Rachel's (Aniston) sister, Jill Greene.

While they're friends in real life, their characters on The Morning Show don't always get along. Witherspoon previously told PEOPLE that it was difficult to fight with Aniston on screen. "I have to say, when we do our fighting scenes, it's really hard not to laugh and crack up, because we have to be so mean to each other," she said. "We just love each other much."

Witherspoon added: "She's literally one of the funniest people I've ever met. Her delivery is perfect on every joke."

As of late, Aniston has been filming Murder Mystery 2, a sequel to the Netflix crime comedy, Murder Mystery, that premiered in 2019.

The second film takes place, at least in part, in Hawaii. On Tuesday, Aniston posted a photo of herself and costar Adam Sandler. "Back to work with my buddy. #MurderMystery2," she wrote.