Overview:

Tom watches and studies films of some of his earlier encounters with Jerry, much like game films; he runs them backwards and stops them so he can study them more closely, all the while scribbling notes. Jerry pulls up a box of popcorn and watches, too. Tom notices Jerry and chases him into his hole. Tom designs a better mousetrap, but Jerry alters the plans, so it doesn't work any better than it did the first time the footage was used, in Designs on Jerry (1955).