Muscle Man invites everyone to High Five Ghost’s birthday party, except for Mordecai and Rigby (as they had accidentally spilled his soda). Mordecai and Rigby try to crash the party, however they are denied access. High Five Ghost’s brother, Low Five Ghost, turns Mordecai and Rigby into ghosts so they can phase through the party tent. However, High Five Ghost and his father tell them that they could get stuck as ghosts, and the only way to change back is to scare someone. Mordecai and Rigby scare Muscle Man, but he suffers from a heart attack. However, Muscle Man rises up and reveals it was all a prank, as a way to get revenge on Mordecai and Rigby for spilling his soda (ignoring that it was an accident). Muscle Man then chokes on his food, so it’s up to Mordecai to perform a Heimlich maneuver on him, so that they are even and have Mordecai and Rigby change back.