Episode 13 - A Fight Against Gravity...Catch Bubbles!:
After Goku passes King Kai's test to make him laugh, the training begins. Goku's first task is to catch King Kai's pet monkey, Bubbles, in a gravity that is ten times stronger than Earth's. King Kai tells Goku that the planet Vegeta, the Saiyans homeworld, had the same gravity as his place and that the two Saiyans that are on the way to Earth are even stronger than King Kai himself! This test reinforces Goku's determination to train even harder to defeat them.