Jennifer Aniston Wishes Friends Costar Lisa Kudrow a Happy 59th Birthday: 'I Love You!'

Lisa Kudrow knows that friends are forever.

The Emmy Award winner celebrated her 59th birthday on Saturday with help from her Friends costar Jennifer Aniston, who paid tribute to Kudrow with some fond throwbacks of the two of them.

"Happy birthday @lisakudrow," Aniston, 53, captioned a photo of them at the 29th People's Choice Awards in 2003. "I love you," she wrote with a GIF of them jumping up and down and cheering as their Friends characters Rachel Green and Phoebe Buffay.

RELATED: Lisa Kudrow Says Jennifer Aniston, Courteney Cox 'Came Running' to Support Her After Mom's Death

Aniston also shared a more recent candid photo of herself kissing Kudrow on the forehead.

Jennifer Aniston/Instagram

Kudrow has said that her son Julian Stern, 24, used to think Aniston was his mother when he visited the Friends set as a kid. "He got a little confused, I know that he was really obsessed with Jen Aniston," she said on Conan last year.

"He'd fly into her lap," she recalled. "Well, she's a love bug, and that made sense. And I was always glad for anyone that Julian felt love for and felt from.

"But then at home, she'd be on TV, and he'd go, 'Mommy!'" Kudrow shared with a laugh. "I'm kind of analytical so I'm like, 'Is this wishful thinking? Do they have some kind of higher soul connection that I don't have with him?' I'm happy for both of them."

Jennifer Aniston/Instagram

The Comeback star previously recalled how Aniston and fellow Friends alum Courteney Cox showed up to support her after her mother died at the beginning of the COVID-19 pandemic as she appeared on SiriusXM's The Howard Stern Show last year.

"These women came running to support, that was really nice," she said. "They came to the funeral, it wasn't a lot of notice, and they were there."

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The trio reunited with their other Friends costars Matthew Perry, Matt LeBlanc and David Schwimmer for the HBO Max reunion special last May. The group starred in the beloved NBC sitcom during its 10-season run from 1994 to 2004.

RELATED VIDEO: Lisa Kudrow Says She Got Rachel on a Friends Character Quiz

Kudrow told PEOPLE of the cast's long-lasting bond at the time: "I feel like we can pick up right where we left off, and no time's passed. We're connected no matter what."

"It's still, to me, one of the greatest jobs I've ever had," Aniston added. "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."