SpongeBob takes him to the Krusty Krab and Goo Lagoon, where the seemingly inanimate bubble inadvertently causes trouble and angers everyone he came in contact with, before revealing he is sentient and living.
He most recently appeared in the episode "Bubbletown."
He is a transparent-colored bubble that is sentient and has the common features of most characters in the series, having a body and separate limbs. Near the end of the episode and in the video Battle for Bikini Bottom, he is seen wearing a hat.
At the Krusty Krab, SpongeBob forces Squidward to remake Bubble Buddy's Krabby Patties several times in order to suit his preferences. According to SpongeBob, Bubble Buddy is lactose intolerant, no cheese, drinks shampoo instead of soda and prefers it regular instead of diet, prefers no crust, ketchup under the patty, pickles to the left, four squirts of ketchup, wheat buns, non-deli lettuce, and farm-raised tomatoes, carnival style - and at some point before eating requires a massage. He also fails to pay for the meal, paying in "bubble dollars," which are not a real form of currency and quickly pop out of existence.
Later on, at Goo Lagoon, SpongeBob and Bubble Buddy continue to make trouble. SpongeBob leaves Bubble Buddy with Scooter, who is buried up to his head in the sand, saying he will unbury him, and Scooter drowns when the high tide comes. When Bubble Buddy "has to go to the bathroom," SpongeBob leaves him in the Port-O-Head for two hours, making everyone else wait. While dancing with Bubble Buddy, SpongeBob inadvertently insults the other dancing beach-goers by saying "shake that bubble butt," which the people take as calling them fat. Bubble Buddy also shakes Pearl's hand, which had just been dirtied by Grubby Grouper, and accidentally cleans it. After all these shenanigans, an angry mob is formed, whom surround SpongeBob and Bubble Buddy.
Just as he is about to be popped by a needle, Bubble Buddy suddenly animates, much to the shock of the everyone (except SpongeBob), and decides to leave Bikini Bottom, saying that "things are getting a little weird around here." A bubble taxi picks him up and he leaves with a suitcase and disappears into the sky. He then says, "Happy Leif Erikson Day!," to SpongeBob.
Six seasons and 11 years after his debut, Bubble Buddy makes his second in-series appearance. He sends SpongeBob a duty to babysit his rather troublemaking son, Shiny Bubble. Bubble Buddy makes only a minor appearance in this episode, only appearing in a flashback, writing a letter to SpongeBob, and in the ending when he picks up his son and thanks SpongeBob before leaving in his bubble plane. This episode also reveals the address of Bubble Buddy.
In this episode, SpongeBob decides to take a trip to Bubbletown. There, he reunites with Bubble Buddy once again. SpongeBob helps the citizens of Bubbletown after repairing Bubble Buddy's vehicle, but soon he ends up popping a lot of buildings and residents in Bubbletown. Bubble Buddy and SpongeBob are then separated for some time as SpongeBob is sent to jail. After Mr. Krabs destroys Bubbletown entirely, Bubble Buddy shows up with a big container, which SpongeBob uses to bring Bubbletown and its citizens back.
He appears as one of the major secondary characters who appear in several of the game's levels. He serves as a tutorial character who explains and teaches SpongeBob new moves as the player progresses through the game's hub sections, which are the Bubble Bash, the Bubble Bowl, and the Cruise Bubble.