Seth Rogen Won't Back Down From Bieber Bashing: He's 'Obnoxious and Ungrateful'

Sorry, Beliebers — Seth Rogen's not apologizing for his infamous Justin Bieber tweet posted after the singer's DUI arrest in January.

On "Watch What Happens: Live" Wednesday, the "Neighbors" star was asked about the Twitter post — which said, "All jokes aside, Justin Bieber is a piece of s--t" — and he stood firmly by what he wrote. Then, he took the whole celebufeud a step further by calling him a few more names.

"Oh, it's because, in my opinion, Justin Bieber is a piece of s--t," the 31-year-old funnyman said with a laugh. "He seems like he is obnoxious and ungrateful and insincere. He puts people's lives in danger with his horrible, horrible behavior. And overall he acts like a piece of s--t."

Well, just watch his whole (hilarious) response to the fan question here:

Rogen's not the only one who has taken to Twitter to weigh in on the smug star, whose antics have been making headlines for over a year and is plagued with legal problems, including two arrests and various lawsuits. In addition to the "This Is the End" star's tersely worded tweet, which was retweeted more than 200,000 times, here are some other memorable Twitter scoldings he's received from his famous peers…

Olivia Wilde is not a fan of Bieber's obsession with going shirtless:

[Related: Justin Bieber's 15 Most Awkward Shirtless Moments]

"Supernatural's" Jared Padalecki had a laugh over his mug shot:

Conan O'Brien has made fun of his bad boy rep:

So has Ricky Gervais:

And Jimmy Fallon, too:

Zach Braff smoked him with a comment about his pot scandal:

Model Chrissy Teigen cut him down to size with a remark about his once-signature side-swept hairstyle:

Drake Bell has been feuding with Bieber for years now, making cutting comments about Bieber's height:

His style:

And graffiti skills:

And Rainn Wilson joked about, well, pretty much everything:

Which celeb's Bieber Twitter crack is your favorite? Let us know in the comments.