As part of the new Horror themed GPK released in stores this week (with a cool looking tombstone for the Bonus Box), there is a 10 card subset of Wacky Packages candies with GPK characters added to them - titled Trick or Treat.
(this is similar to the subset that was in the 2016 Prime Slime set, where just the Wacky character is swapped out for a GPK one)