This friendship is anything but shallow.

As for the proof? Lady Gaga, who starred alongside Bradley Cooper in the 2018 remake of A Star is Born, stepped out to support the actor for the Los Angeles premiere of his latest movie Maestro. And as Bradley explained, he'll always remember their bond this way.

"It means the world to me," he told E! News correspondent Keltie Knight at the Maestro premiere Dec. 12, "also because I'm really excited for her to see the movie. She's a dear friend and we went through such an incredible experience together, so you just want to share the art with each other." (For more with Bradley, tune into E! News tonight, Dec. 13, at 11 p.m.)

Though his roles as troubled singer Jackson Maine and the biographical portrayal of Leonard Bernstein are years apart, both proved to have its own set of challenges. But for the Golden Globe winner, one film was undoubtedly more intense than the other.