butt on fire
Used to describe a character's butt catching fire, or when their butt has just been burned.
Usually depicted as a character sprinting forward trailing flames and smoke, or leaping upwards out of lava.
Often used in games as a comical player death, but often used in artwork as a precursor to exposure or any other humiliating mishap.
Example being of a character trying to act cool just after getting burned only to turn around and reveal their pants have burnt up enough to expose their butt.
This tag implicates fire (learn more).