Ah the possibilities...
Some possible costumes:
The Pirate and his Wench
The Mob Boss and his Gun Moll
The stern Professor and his bubble headed student (one must have a ruler to complete the costume)
The overly eager nurse and her patient
The animal tamer and the lioness (complete with chair and whip)
The Quidditch Coach and the new player
The snake charmer (Harry's costume would consist solely of a wicker basket around his manhood from which the woman can charm the snake)
Adam and Eve (a well placed leaf can lead to wonderful adventures)
The By-The-Book Auror and his Prisoner
The Manservant and the Queen
The classic Sailor on a three day pass meets the exotic and mysterious Lady of the Evening
The Conquering Mongol and his captured slave
Of course the real challenge deals with what witch would go along with what costume.
Shawn (a.k.a. cloneserpents)
And you guys wonder why I said I wanted to make this open to others to write?
Love the snake charmer. I am trying to come up with some costumes that are like the punny ones but magical.
Ex. A plug and a socket, bacon and eggs.
Hmmm, a broom and a polishing kit?