In 1981, Topps Chewing Gum Inc. issued a set of mini movie posters in their gum packages which were the replicas of various popular one sheets. 12 different posters measuring 12x20 were issued. Each poster was folded down 5 times to be able to fit into the 2.5" x 3.5" pack.
Here is the list of what was issued:
Special thanks to Quadbod for additional information