Bill Hader reveals the worst-behaved 'SNL' musical guest during his tenure

Working with celebrities isn't all sunshine and roses. Take it from two Saturday Night Live alums.

During a recent appearance on Watch What Happens Live, Bill Hader and Jay Pharoah revealed the "worst-behaved" musical guest they'd ever encountered during their time on the show: Justin Bieber.

"He was in a bad place," Hader told Andy Cohen as Pharoah agreed. "Maybe he's in a better place, but then he was in a very – it was rough." As he recalled it, Bieber "just seemed exhausted or at the end of his rope."

And while a hot young celebrity acting out is hardly shocking, Bieber stood out because most SNL guests don't act that way. "Everyone's usually on great behavior," said Hader.

The two were referring to a 2013 episode during which Bieber appeared as both the host and the musical guest. (Bieber had been on the show once before as a musical guest in 2010, before Pharoah joined the cast.)

Although the SNL vets didn't go into detail about Bieber's antics in this interview with Cohen, Hader has spoken about his experience with the pop star before. In 2013, shortly after his departure from the show, Hader spilled the beans to Howard Stern.

"Justin Bieber showed up with like 20 guys," he said at the time. "And you know, when you're backstage, it's a very, small constricted place. He had a guy holding a slice of pizza, a guy holding a Diet Coke. You were going around stage and trying to fight around all these people to get dressed."