This is such a good example of taking an old idea and turning it into something modern. I personally felt the "Gag Bag" never quite fit into a modern world. However, making the bag bigger and turning it into a trick or treat bag makes this prop instantly recognizable.
The Gag Bag and the Trick or Treat Bag are both MC gags. The MC comes on and says that someone forgot their trick or treat bag and begins to describe it. This is where the performer takes over and his reaction to the bag can get some really good responses from the audience. Each time the MC tries to describe the bag, it changes and the MC has to change his description along with it. At the end of the effect spring flowers or a selected card can be pulled out of the Gag Bag (or Trick or Treat Bag), depending on how you routine it.
I would think a better way to present this would be to have a couple kids run on stage and say "trick or treat" to the MC. The MC, looking stunned at his act being interrupted, decides to ask what the kid has inside the bag. The MC looks, and finds that the inside of the bag keeps changing until finally he hands the kid back his bag and it now has a completely different outside and inside then when the kid first brought it up.
Currently this is a special order from Abbott's and you won't find it in their catalog.
Not the strongest effect in the world, but in the right hands a good MC can get a lot of laughs out of this product. Also works well at kid shows, have a few candies in the bag to hand out to the kids at the end always works well. The gag bag is not seen that often in today's shows but as far as I know converting it into a trick or treat bag is an original idea and maybe this classic MC gag might find a new home at Halloween.