You choose one or two of your characters and say who they dress up as. Provide details, and references (eg. if I say that Cody is dressing up as Willow, then I should provide a few pictures of Willow's costume and make it clear whether he's Willow from "Buffy the Vampire Slayer" or Willow from "Willow" the movie.)

Then take your character and a few others and draw out a comic or two about the party. However much you want. If it's a single one-panel thing, that's fine. If it's more than that, that's fine too. Jokes optional. You don't have to draw a comic (but we'd prefer it if you did). The comic you draw doesn't have to feature everbody's characters - you could do something with
just your characters, or something with just someone else's characters.