Kicked off the set of the space movie Gian and Suneo are shooting, Nobita starts filming his own with Doraemon and Shizuka and finds what looks like a toy rocket. That night its pilot turns up in his room: Papi, a tiny humanoid who is the president of the planet Pirika, which has fallen to the dictator Gilmore. Shrinking themselves with one of Doraemon's gadgets to play at Papi's size, the children promise to keep him safe, but Gilmore's intelligence agency, the PCIA, has already followed him to Earth.