Bulma used the PP Candy, disguised as a vitamin, to make Oolong obedient. She tricks him into eating it, but after he eats it, any time she yells "Piii Piii!", he would have stomach cramps and diarrhea. In other dubs, she yells "Piggy!" and in the manga she whistles "Swee!" (a call used by farmers to let pigs know when it's feeding time).
Video game appearance
"Ugh... I've got a really bad stomachache after whistling... Maybe there was something in that candy I ate earlier."
— Bentora in Dragon Ball Xenoverse 2
In Dragon Ball Xenoverse 2, it is implied that the Majin Time Patroller Bentora accidentally ate some while investigating the Capsule Corporation time rift anomaly, though it only gives him a really bad stomachache implying that Majins are only partially effected presumably due to them having a stronger digestive system (as they can survive eating Poisonous Mushrooms in the same game).