Bubbles is the monkey pet of the North Kai, also known as King Kai. He plays a crucial role during King Kai's training sessions, specifically in one of two endurance tests. Trainees are tasked with chasing Bubbles to catch him, which forces them to push their limits in gravity ten times that of Earth's. Goku spends 40 days working on this challenge, while Piccolo, who was later killed by the Saiyans Nappa and Vegeta and sent to train with King Kai in the Other World, manages to catch Bubbles almost effortlessly. This is because, during the year Goku spends running Snake Way and training with King Kai, Piccolo has been training both alone and with Gohan. King Kai exclaims in surprise that the test was not meant for someone of Piccolo's caliber but for Yamcha, Tenshinhan, and Chiaotzu.
Bubbles meets his end when Semi-Perfect Cell self-destructs on King Kai's planet after being teleported there by Goku.
(Source: Dragon Ball Wiki)










