AUSTIN, Tex. — Surprises abounded at this year’s South by Southwest film festival, with movies featuring depraved demons, devilish doppelgängers and sadistic senseis all doing despicable things. And yet, one of the most gasp-worthy moments was hearing the tween actor Jacob Tremblay use the F-word in the first five minutes of “Good Boys.” It wouldn’t be the only time in this comedy about a wild day in the life of a few sixth-graders, and it was one of several breakout titles worth knowing about as the film portion of the festival comes to a close on Saturday.

“If I’m being honest, I am shocked and appalled,” Tremblay joked during the post-screening Q.& A., and added referring to his director Gene Stupnitsky, “Gene told me this was going to be a PG-rated family movie. He lied.”

Image Tremblay, right, with Seth Rogen, one of the producers of “Good Boys,” at SXSW. Credit... Matt Winkelmeyer/Getty Images For SXSW

The movie was right at home at a festival that has turned into something of a testing ground for the hit potential of Hollywood comedies. The audience applauded the comic timing of Tremblay and his co-stars, Brady Noon and the scene-stealing Keith L. Williams, and that positive reaction along with a recently released red-band trailer featuring one of the movie’s producers, Seth Rogen, has fueled social-media interest. “Good Boys” opens nationwide in August.