Jiggle Billy was first seen in Dumber Dolls as a toy Meatwad wanted Frylock to buy for him. His $149.99 price tag (apparently having something to do with his "expensive night vision goggles - for night jiggling!") caused Frylock to buy Meatwad Happy Time Harry instead, whose nihilistic, suicidal demeanor and surly attitude eventually made Meatwad depressed and bitter, prompting Frylock to splurge and buy Jiggle Billy in an attempt to improve Meatwad's attitude. By this point, it's already too late, as Happy Time Harry promptly begins mocking and berating Jiggle Billy, making him depressed too, forcing him to admit he "doesn't know why [he] has these goggles" and culminating in him shooting his head off with his blunderbuss in a suicide attempt, which he survives apparently no worse for the experience except for still being "real depressed".
Jiggle Billy is a shoeless backwoods hillbilly with a red shirt, a moonshine jug, a blunderbuss style gun, and some patchwork denim pants, as well as his unnecessary and expensive night vision goggles that apparently account for his very high price tag. He is obsessed with jiggling, which he talks about endlessly and does every few seconds along with a little banjo song.
Since then, Jiggle Billy has popped up in a few episodes besides Dumber Dolls, such as The Last One, where the Plutonians had him as a member of their meeting since they weren't invited to the Mooninites' meeting like everyone else was. He also appears in The Clowning where Shake throws his headless body into the air for Carl to juggle along with Frylock's microscope after Carl turns into a clown, and in The Dressing in the beginning when Meatwad pulled his headless body out of his body, followed by Squirrley.