Why can't *I* go trick-or-treating?

Great, just great.  This morning I got dragged to the vet, and while Nestle pranced around getting high-fives from all the staff, I was shuttled off to a room where they poked my leg with a 16-inch (maybe 20-inch) needle.  And now I'm stuck lying in the kitchen while Thelma flies around the house on a broomstick & gives free candy to dwarves begging at the door.  What's the big idea?  Where's MY treat?