Balloon Boy, often abbreviated as BB, is a human child-like animatronic and one of the toy animatronics that first appeared in Five Nights at Freddy's 2. He wearing blue pants, a red and blue vertical striped shirt, and brown shoes; holding a yellow and red striped balloon, and a "Balloons!" sign. BB resembles a human, with a round body, peach skin, large blue eyes, orange triangle nose, reddish-brown hair, and a toothy smile. Like the rest of the new animatronics, his cheeks are flushed and rosy. Balloon Boy's few lines throughout the series suggest that he seems to be a shy character, and judging by his laugh, he seems cheerful but more on the mischievous side. Often considered troublesome and wreaking havoc on players, he acts like some sort of bully, showing no remorse for his actions, but gradually enjoying them.

Phantom Balloon Boy is an illusion of a burnt and damaged BB first appearing in Five Nights at Freddy' 3. The Phantom BB is basically the same model as the BB in Five Nights at Freddy' 2, but he has no eyes and has two white buttons (like the office in Five Nights at Freddy' 2, although that could also be a lighting error ). Instead, he has small, glowing white pupils similar to Springtrap and other Phantoms, and lacks his "Balloon!" logo and balloon. His rosy cheeks seemed to be dyed dark green. The Phantom BB appears to be charred or burnt, possibly signaling the burning of the attraction.

Nightmare Balloon Boy is one of the nightmare animatronics in the Five Nights at Freddy's series, debuting in Halloween Update expansion (both Standard and Halloween Edition) for Five Nights at Freddy's 4. The Nightmare Balloon Boy has a similar appearance to the original BB, but with a more menacing design. His large, pointed teeth in his large mouth, as well as his dark blue eyelids and gums, long claw-like fingers, and more sinister eyes with red irises and narrow gray veins, all make him look creepy. He also has a red and purple striped hat and shirt instead of his usual red and blue stripes. The pinwheel on the top of his hat is also blue instead of orange, with a yellow button on top. Two of his buttons are indigo instead of the original BB's black buttons. His brown hair is slightly shorter than his original hair. His blue pants are lighter in color. On closer inspection, the Nightmare Balloon Boy appears to be wearing white socks. His shoes are exactly like his original shoes, although they appear lighter in color. Interestingly, the Nightmare Balloon Boy looks flawless.