Ahead of the 20th anniversary of their film, 13 Going on 30, Hollywood star Mark Ruffalo has nothing but incredible things to say about co-star Jennifer Garner.

We had just a wonderful chemistry together: Ruffalo on Garner

The actor explained what initially brought him to the project and why it was the “wonderful chemistry” he had with Garner, 51, that hooked him.

“It was my first kind of studio film and, I’d been doing pretty small indies up to that point. Gary Winnick, our director, said, ‘I want to do a small indie but in a rom-com studio film,’” he said, adding that Winnick told him he would be opposite the Alias actor.

“It was Jen Garner, who is just magical, and we had just a wonderful chemistry together,” the Avengers star said. The film released in April 2004 and became an instant classic, boosting Ruffalo and Garner’s own careers astronomically.

He credits 13 Going on 30 with helping him to reach the next stage in his career and being cast in elevated roles. “I think people started to see me in a lot more different kinds of elevated roles than what I’d been playing up to that time,” Ruffalo said.