Instead of milk and cookies, leave him a salad, and a note explaining that you think he could stand to lose a few pounds.
While he's in the house, go find his sleigh and write him a speeding ticket.
Leave him a note, explaining that you've gone away for the holidays. Ask if he would mind watering your plants.
While he's in the house, replace all his reindeer with exact replicas. Then wait and see what happens when he tries to get them to fly.
Keep an angry bull in your living room. If you think a bull goes crazy when he sees a little red cape, wait until he sees that big, red Santa suit!
Build an army of mean-looking snowmen on the roof, holding signs that say "We hate Christmas," and "Go away Santa."
Leave a note by the telephone, telling Santa that Mrs. Claus called and wanted to remind him to pick up some milk and a loaf of bread on his way home.
Throw a surprise party for Santa when he comes down the chimney. Refuse to let him leave until the strippers arrive.
While he's in the house, find the sleigh and sit in it. As soon as he comes back and sees you, tell him that he shouldn't have missed that last payment, and take off.
Leave a plate filled with cookies and a glass of milk out, with a note that says, "For The Tooth Fairy. :)" Leave another plate out with half a stale cookie and a few drops of skim milk in a dirty glass with a note that says, "For Santa."