It’s no secret that Seth Rogen isn’t exactly Justin Bieber’s biggest fan — and not just because Seth’s on the outside, judging Justin’s recent behavior like most people. Nope, Seth has had a few run ins with the Biebs that have helped form his opinion on this troublemaking whippersnapper, and now, he’s ready to enlighten us.

When Seth sat down with Howard Stern this week, he addressed his distaste for the 20-year old singer — and how it all happened. And in true Howard Stern interview fashion, Seth doused his diatribe with an extra helping of profanity.

“I met him a few times,” Seth said. “He’s a good example of someone who you meet, who you think you’re going to hate, and then you get to hate him … You meet him and he lives up to every one of your expectations.”

So what exactly went wrong that Seth is so anti-Justin? It all began when Justin’s career was first taking off and both guys were backstage at the same German talk show and Justin asked to meet Seth… and then acted as if he wasn’t interested in talking to him at all.

“What the f—k? I don’t want to meet you!” Seth said. “Don’t act all nonplussed to meet me. I didn’t want to meet you.”

And a few years later, when Seth and Justin met again? It only got worse.

“I saw him again at, like, an MTV Awards show. He literally had a snake wrapped around his f—king wrist that he was wearing,” Seth said. “I talked to him for like five minutes. No humility, no awareness, no sense that, ‘I appeal to young, young people, maybe a grown man who works in comedy doesn’t f—king give a sh—t about me. Maybe I should act in such a way that perhaps this isn’t the great experience of his f—king life.”

The Seth/Justin feud: A battle between egos or an actual, legitimate case of two people who just don't like each other? The world may never know.

Source: Howard Stern via ABC News