Meryl Streep and Cher Kiss at the 'Mamma Mia' Premiere in London -- See the Pic!

The Oscar winner certainly made a statement while promoting their new film.

Meryl Streep and Cher certainly made a statement at the London premiere of their new film, Mamma Mia! Here We Go Again.

While walking the red carpet at the Hammersmith Apollo on Monday, the longtime pals stopped to pose for pictures together -- Cher, 72, in an all-black ensemble, and Streep, 69, in bright blue. At one point, the two spontaneously turned to each other, sharing a kiss on the lips.

Stuart C. Wilson/Getty Images for Universal Pictures

ET caught up with Cher (who portrays Streep's onscreen mother, Ruby Sheridan, in the sequel) one day ahead of the premiere, where she had nothing but amazing things to say about her co-star. The two first worked together in 1983 on Silkwood, a drama directed by Mike Nichols.

"We've stayed friends all these years. I cannot believe that, but that was my first film, and she helped me," Cher recalled. "I mean, she was unbelievable, because I had no idea what I was doing."

"It's great to see her [again]," she added.

Cher also told ET that it was a bit funny learning that she'd be portraying Streep's mother onscreen, seeing as the two are only a few years apart. 

"I didn't really think it had much to do with anything, you know? I just thought, 'It's a part of the character,' but it wasn't like, 'Oh, what can I do to be her mother,'" she explained. "I just thought it was cool."

ET also exclusively sat down with Cher last month, where she teased what audiences can expect from her character.

"I come in in a helicopter, and then I land and I come walking up with a cane," she said. "I'm different."

Mamma Mia! Here We Go Again hits theaters on Friday. In the meantime, watch the video below to hear more on Streep and Cher's longtime friendship.