We already know that farting astronauts are serious business, but the fact is that even the best-trained moonwalker can't stop themselves from passing gas. Apollo 16 astronaut John Young didn't just fart prolifically while on the moon, he colorfully described his flatulence during a mission debriefing.
I'm not sure whether the embedded recording above is an actual audio recording of the exchange between Young and NASA Mission Control or whether it's a reenactment based on the mission transcript, but Young did indeed toss off a "fuck" or two when describing his OJ-based indigestion to his crewmate Charlie Duke — while the mic was on to Mission Control back home. (And after all the trouble NASA went through to keep astronauts from swearing over their microphones.)
Mary Roach actually mentions this incident in her book, Packing for Mars, with this addendum: The governor of Florida was less than pleased that Young was blaming his gas on Florida's signature crop. After the press reported on Young's candid discussion of his bodily functions, the Florida governor assured the public that it was not real citrus, but an artificial substitute, that was responsible for Young's swear-worthy gas.
It was actually all the potassium he was downing that caused the flatulence. During the Apollo 15 mission, the astronauts suffered from a potassium deficiency that caused James Irwin to suffer a cardiac arrhythmia and David Scott to suffer less severe heartbeat irregularities. All that gas was probably a small price to pay for keeping the astronauts' tickers on track.