The Shadow on the Moon at Night or Oogie Boogie Shadow is a fictional shadow that appears in the beginning of the film Tim Burton's The Nightmare Before Christmas on the town's moon. It's suggested that the shadow belongs to Oogie Boogie the film's antagonist, because his shadow is identical to the one on the moon.
The Shadow also seems to have the ability to dissolve into millions of terrorizing bats. Just like Oogie Boogie spits out bugs.