From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Bubbles (バブルス, Baburusu; FUNimation "Bubbles", Viz "Bubbles") is an Ape and North Kaio's pet. He serves a special purpose during North Kaio's training lessons, particularly one of two endurance tests where trainees are instructed to chase after Bubbles in an effort to catch him.
Son Goku first thought Bubbles was North Kaio and he thought he would have to act like a Monkey to begin the training until the real King Kai showed up. Goku was forced to catch Bubbles as part of North Kaio's training. This forced Goku to push himself in a gravitation 10 times that of Earth. Goku spends 40 days working on this test, while Piccolo, who is later killed by Nappa and Vegeta and is sent to train with North Kaio in the Next World, manages to catch Bubbles almost effortlessly (due to Goku spending a year running on the Serpentine Road and training with North Kao while Piccolo had been training both in solitude and with Son Gohan). This causes North Kaio to yell out that Piccolo should know that Bubble's test was not meant for him, but for Yamucha, Tenshinhan, and Chaozu.
Bubbles appeared in Dragon Ball Z: Bojack Unbound in scenes in the Next World where he accompanied North Kaio, Goku, and Gregory, as well as Broly: The Legendary Super Saiyan in scenes in the Next World where he accompanied North Kaio. He also made a cameo in Dragon Ball Z: Bio-Broly telling Goku that Broly was acting up in Hell and that Paikuhan and Goku needed to take care of the situation. He, Gregory, and North Kaio also appeared at the banquet in Dragon Ball: Ossu! Kaette Kita Son Goku to Nakama-tachi!!.
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- The name Bubbles may be a reference to the late Michael Jackson's pet monkey, Bubbles.
- Bubbles is the first character to meet Goku on North Kaio's World.
- Bubbles, Gregory, and a Fish in Grand Kaio's flashback are the only animals to be shown in the Next World.
- North Kaio says that it took Goku three weeks to catch Bubbles, while Piccolo catches Bubbles in approximately 5 seconds because he is accustomed to intense gravity. He is actually just well adjusted to heavy weights because he wears his weighted clothing almost every day of his life.
- Besides eye color, snout, and size, Bubbles resembles the Great Ape transformation.