A condition brought on by an intense hangover. Even the most mundane situation or comment suddenly seems hilarious. It is thought to be triggered by a combination of sleep deprivation and the sufferer's desperate need to be distracted from how terrible they are feeling.
Guy 1 - "What is she creasing herself over?"
Guy 2- "Don't know. It's probably nothing though. She's got a severe case of hangover hilarity today."