Sakkaku Scale by Tenyo

This is a clever combination of a traditional optical illusion and new thinking. It builds on the plot of the traditional boomerang trick. The magician shows two plastic strips with cats on them. To the eyes of the spectators, it appears that the two strips stretch and shrink. For the climax, the magician proves that the two plastic strips have actually changed size. The trick was originally available in Japan from Tenyo. Complete with instructions in Japanese and English.