Do you still remember the Halloween day in Big Bang Theory?

The Halloween day in 2012 in Big Bang Theory comes from No. 7 sets, season 5.
It's called The Good Guy Fluctuation. This set is one of the most funny in Big Bang Theory. Leonard, Howard and rajesh dressed up as a ghost when Sheldon worked,which maked Sheldon scared to death, so Sheldon decided to revenge the guys Sheldon scared his friends on Halloween in the most terrible way, but....