In fact, the actor has been rather vocal about his feelings on the pop star while promoting his new flick, "Neighbors," this past week. His ongoing shots finally triggered a response from Justin, who hit Twitter to say he was sorry he didn't "bow down" to the movie star when they first met.
Up until that moment, it seemed to be a one-sided beef, with Seth calling Justin everything from a "piece of sh--" to "obnoxious" and "ungrateful." So how did this all begin? Well, we went back over the last few months and complied everything Seth has said about the Biebs.
January 23, 2014: The Tweet That Started The Fued
Following Justin's arrest for drag racing and a DUI in Miami back in January, Seth took to Twitter to share his opinion of the incident.
March 12, 2014: "Watch What Happens Live"
Seth sat down with Bravo's Andy Cohen on "Watch What Happens Live" to clear up that tweet, which actually needed no clearing up at all.
"He seems like he's obnoxious and ungrateful, insincere, and he puts people's lives at danger," Seth said. "And overall, he acts like a piece of sh--."
May 5, 2014: "The Howard Stern Show"
Two months after Rogen's last comment, Howard Stern got Seth going again, this time discussing meeting Justin for the first time. The pop star apparently requested an introduction and then played nonchalant when the pair appeared on a German radio talk show a few years back.
"What the f--k, I don't want to meet you! Don't act all nonplussed to meet me. I didn't want to meet you. I was totally cool with not meeting you," Rogen remembered thinking, adding, "I was like, ‘He's a little bit of a mother----er. Whatever. He's a bit of a dick."
Seth wasn't done ranting on the Biebs just yet, he also recalled his run-in with Bieber at the 2011 Video Music Awards.
"He literally had a snake wrapped around his f--king wrist that he was wearing, like a live snake as an accoutrement. I was like 'What the f--k?' I talked to him for like five minutes," Rogen said. "I just remember thinking, 'F--k this kid. He's a piece of sh--.'"
May 7, 2014: "The Today Show"
Stopping by the "Today" show, Seth was once again put on the hot seat regarding the pop star. He told Matt Lauer that given that he's a grown man, it shouldn't be all that controversial that he doesn't like the singer.
"It would be much weirder if I did like Justin Bieber," the actor said. He then turned to the off-camera crew and added, "None of these people in this room like Justin Bieber. I can guarantee you that."
May 7, 2014: "The Daily Show With Jon Stewart"
Seth took his hate for Justin from the morning shows to late night, sitting down with Jon Stewart, who confessed that he had to break the news to his daughters that their favorite actress, Selena Gomez, "hangs out with an awful guy." Seth came back saying that he doesn't have kids, but he does have a dog that "doesn't need to know" about Justin, but that "if there's one thing a dog can smell, it's an a--hole."
May 8, 2014: Justin Bieber Fires Back
It seems Justin had finally had enough.