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The fantasy romantic comedy - 13 Going On 30 - starring Jennifer Garner and Mark Ruffalo celebrated its 15th anniversary this week.
It turns out Ruffalo, 51, had no idea that his Avengers: Endgame co-star, Brie Larson, had a role in the hit teen film.
Carpet - World - Premiere - Endgame - Monday
While on the red carpet for the world premiere of Endgame on Monday, an Entertainment Tonight reporter showed a stunned Ruffalo a photo of Larson in a scene from the movie.
'She was a mean girl, oh my god! That's amazing,' Ruffalo began with a huge smile on his face.
'How cool I didn't know that,' via People.
Larson played one of the so-called Six Chicks in the film's 1980s scenes, which means she didn't share any screen time with Ruffalo.
'We didn't work together [on 13 Going On 30],' he added, while...
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