Zach Galifianakgets forthcoming in new Rolling Stone piece. (Stephen Lovekin/GETTY IMAGES)

Now we know why Alan, Zach Galifianakis’s socially challenged characters in “The Hangover” movies, won’t get married in a potential third installment in the series. He’ll be too busy escaping from a mental institution.

In a Rolling Stone cover story on Galifianakis, to be published next week, the actor says he is “getting fricking phone calls already” about doing a third “Hangover.” And he says the plot will stray from the format of the first two, instead focusing on how Alan’s buddies — Phil (Bradley Cooper), Stu (Ed Helms) and presumably Doug (Justin Bartha) — break him out of a mental hospital.

Naturally, that’s not the only fun tidbit Rolling Stone has teased from the interview.

Apparently at the Vanity Fair/Bloomberg party that followed this year’s White House Correspondents’ dinner, he introduced himself to Jane Lynch, Jesse Tyler Ferguson and their significant others by saying, “Nice to meet you! I didn’t realize it was Gay Night by the swimming pool.” He meant it as a joke. Apparently it was not taken that way.

While working briefly as a writer for “Saturday Night Live,” he also once tried to pitch a sketch that involved host Britney Spears spontaneously bleeding from the mouth. Spears also was not amused.

And when his future “Between Two Ferns” guest Sean Penn offered Galifianakis a role in “Into the Wild,” he told the actor-director he had an appointment at Arby’s but Penn should, “send my Jews the script.”

I can’t wait to see what sort of lines Galifianakis improvs during that stay in the mental institution.