Host for 'Saturday Night Live' on Jan. 13, Sam Rockwell.
Jesse Grant/Getty Images

Sam Rockwell gets really, really excited about science.

While this weekend's Saturday Night Live host was conducting experiments as Mr. Science, with Cecily Strong and Mikey Day, the Three Billboards Outside Ebbing, Missouri actor got an F-bomb by the censors. 

Disgruntled with Strong and Day's characters, Rockwell said, "You guys can't be this (expletive) stupid." Twitter users were quick to highlight the NSFW moment.

Though Rockwell isn't the first to slip up. When Kristen Stewart took a turn at hosting in February 2017 she also let the expletive slip by.

"OK, so we've got a great show," she said at the time, alongside cast members Aidy Bryant and Kate McKinnon, "and I totally care that I'm here 'cause it's the coolest (expletive) thing ever."

When Stewart realized her flub, she immediately put her hand over her mouth.

More: Bill Murray, Fred Armisen return to 'SNL' for the show's 'Morning Joe' cold open

More: 'Three Billboards Outside Ebbing, Missouri' leads Screen Actors Guild nominations