Sam Rockwell's vulgar ad-lib on 'SNL' has Twitter buzzing

That’s right, the “Three Billboards Outside Ebbing, Missouri” star dropped the F-bomb during his very first sketch.

The cringeworthy incident occurred during a PBS parody skit called “Science Show” that also featured regular “SNL” cast members Cecily Strong and Mikey Day. Rockwell plays a Bill Nye-esque science teacher who attempts to teach two of his more intellectually challenged students about the wonders of science using experiments.

In fact, Strong and Day played dumb so well that Rockwell couldn’t help but go off-script and dropped the vulgar expression.

Needless to say, the great minds over at Twitter had a field day:

Here is the skit, with the offending word bleeped out: