Mark Ruffalo Had The Cutest Reaction To Learning Brie Larson Was In '13 Going On 30'

The actor found out on the red carpet for the premiere of his latest film with Larson, "Avengers: Endgame."

Mark Ruffalo had no idea his “Avengers: Endgame” co-star Brie Larson also appeared with him in the 2004 film “13 Going on 30.”

Ruffalo apparently learned about Larson’s role as one of the “Six Chicks” in the 15-year-old movie on Monday, when an “Entertainment Tonight” interviewer showed him an old photograph.

“She was a mean girl! Oh my god. That’s amazing. Wow, I didn’t know that,” exclaimed Ruffalo with a laugh at the Los Angeles premiere of “Avengers: Endgame.” “How come I didn’t know that?”

Ruffalo’s Matt Flamhaff and Larson’s Six Chick never appeared on screen together in “13 Going on 30,” which is likely why Ruffalo was unaware of the connection. The movie, about a girl who makes a wish on her 13th birthday and wakes up 30, co-starred Jennifer Garner as big-time magazine editor Jenna Rink.

Larson told “Entertainment Tonight” she remembered being captivated by the way the cameras moved during filming, and how the finished movie was so different than what she imagined. It was “the moment I realized that I really wanted to direct,” she said.

Many people on social media confessed that they, too, had been unaware that Larson was a Six Chick.