Seth Rogen didn't like Zac Efron when he first met him

Los Angeles - Seth Rogen thought Zac Efron was a "little fucker" when he first met him.

The Neighbors star admits he wasn't impressed by his co-star when he first bumped into him eight years ago, but he's since changed his mind after working with him on the new upcoming comedy film.

Speaking to PEOPLE.com, he said: "I was expecting to not like him very much when I first met him. The first time I met him I assumed he'd be a little fucker, but that was eight years ago. I was proven very wrong because he's a sweet, nice guy ... He was just so nice, cool and very self-aware and self-effacing and endearing, and all those things that make someone hard to hate."

However, Zac - who shot to fame after landing the leading role in Disney's High School Musical in 2006 - was determined to make a good impression on Seth, 32, because he saw him as an inspiration.

Zac, 26, explained: "I really made some extra effort, and after a while I think I wore him down a bit. I've respected Seth since the first movie that I saw him in. He rebranded comedy, and I identified with it, every single part of it: mind, body and spirit. That's how I want to be."