The guys had each worked with Janssen on separate films before they were both cast in hit legal drama "Ally McBeal" in the early 2000s, and the actress was convinced they would have a lot in common.
"We had both just done a movie with Famke Janssen, who is awesome, and she said we'd both be best friends; she said we'd get along great," Hopkins shares.
However, he wasn't so sure about Janssen's prediction when he initially met Marsden.
"So I came in (to the set of 'Ally McBeal') with expectations - that's a problem," he continued. "So I met him, we'd been there for about a month, and I was like, 'I mean, he's fine...' and then one day we had a day where we only filmed together, and by the end we were like, 'Famke was right. She was right!'"
They have been best buds for close to two decades, and the "Cougar Town" star admits the time has flown by.
Hopkins said, "I can't believe it's been that long ago, because he (Marsden) had just had his first son, Jack, and he's 18 now. We're just like, 'How can that be?'"
Janssen worked with Marsden in four of the "X-Men" movies from 2000, while she co-starred with Hopkins in 2000 comedy/drama "Love & Sex".