Bad, Bad Rubber Piggy

Zim finally finishes one of his self proclaimed brilliant inventions, a space-time-object-transfer device, in which he plans to send a giant robot into the past in order to put an end to Dib once and for all. However, when the robot isn't compatible with the temporal field, he throws a rubber pig into the vortex instead, which turns out to be compatible and it causes Dib to crash his tricycle in the past. Zim decides to send many more rubber pigs into Dib's past, which ultimately affect him in the future; though when Zim overdoes himself, he discovers that history isn't something that should be messed with.