Man, I reek of booze, and I can't remember a thing. Where am I? Oh God, looks like I'm on the what did I do last night page! Might be a Noodle Incident where not even the characters know or remember what happened. Often, but not always, involves drugs or alcohol. Strictly speaking it doesn't have to be a night. It can be any alcohol or drug-induced craziness plus memory block. Getting a tattoo or joining the Armed Forces is a common outcome, as is the ever-popular Bedmate Reveal. If they're in Las Vegas, an Accidental Marriage is likely. See also Bedmate Reveal, Did They or Didn't They?.