"I taught him everything he knows," Garner jokingly wrote on Instagram Saturday. "Happy Birthday, Bradley. Go get 'em tomorrow. We are all so proud of you."
A Star Is Born, Cooper's first film as director and the third remake of the 1937 classic, was nominated for five Golden Globes, including Best Motion Picture — Drama. Cooper himself was nominated for Best Actor and Best Director. His co-star, Lady Gaga, earned nominations for Best Actress and Best Original Song as co-writer on "Shallow."
Before Cooper earned his breakout role in The Hangover, the 44-year-old appeared in minor roles in film and television. His biggest TV role was as Will Tippin on all five seasons of Alias, opposite Garner. Since the show ended in 2005, Garner and Cooper have remained friends, with Garner even among the speakers at the American Cinematheque Awards in November to honor him.
During her speech, Garner said she was one of the first stars to meet Cooper when he arrived in Hollywood.
"I took him home and made him dinner… I'm still making him dinner," she joked, reports Entertainment Tonight.
"There is something about people who are the same in success and failure that makes us love them," Garner continued. "Tells us, we know the very heart of them. I know the heart and stomach of Bradley Cooper."
Garner later added, "Bradley, what's happening to you now is a pure joy to those who know you, especially to those of us who've known you from the start. It turns out you weren't just handsome all along. You were also a wonder, and you are welcome at my table anytime."
Garner looks back fondly at her time on Alias and often talks about wanting to do a revival. In October, she told The Hollywood Reporter she would be "very, very angry" if she was not called back to make a cameo on a reboot, if one ever happens.
"I've heard that there's an Alias reboot happening, but no one's talked to me about it. I mean, it would be totally different," Garner said at the time. "But if they didn't have me on as a guest, I would be very, very angry. But I can't imagine it being that serious yet because I haven't heard anything about it at all."
While no plans for an Alias reboot are concrete yet, Garner has signed on to work with creator J.J. Abrams again to star in an Apple series titled My Glory Was I Had Such Friends.
Garner starred as Sydney Bristow on ABC's Alias, and earned a Golden Globe for her performance in 2002.
The 76th Golden Globe Awards start at 8 p.m. ET Sunday on NBC.
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