Big Bang Theory, "The Spectral Inheritance Principle"

Howard inherits a mansion from his rich uncle under the condition that he stay there for the whole night. Did we mention that the house is haunted? The rest of the gang agrees to stay the night with him in order to disprove the existence of spooky scary ghosts. The Big Bang Gang™ splits into groups to investigate the paranormal happenings. Sheldon and Leonard eat a comically large sandwich then hide in a vase after Howard’s dead mother chases them through the non-euclidian upstairs hallway. Penny and Cousin Leroy fall through a trap door into a cellar full of corpses. Howard is mysteriously absent throughout most of the episode.