Corpsing

Corpsing is British theatrical slang for unintentionally laughing during a non-humorous performance. In North American TV and film, this is commonly referred to as breaking character or simply "breaking". The origin of the term corpsing itself is unclear, but may come from provoking an actor into laughing while portraying a corpse. There are many examples of corpsing, such as performers portraying sleeping or unconscious characters.