Bill often takes Stan's place when there are things he doesn't want to go to, such as Steve's baptism or cooking classes with Francine.
When Stan was faced with the dilemma of whether to go to the high school reunion prom with Betty Sue the Homecoming Queen, and saving his marriage with Francine in "It's Good to Be the Queen", Stan called in Bill to take Francine out to dinner while he went to the prom. But Francine decided to go to the prom, making things a bit complicated, since Stan decided to give up his dream rather than lose his wife. When Francine discovers Stan's deception and is confronted with both Bill and Stan simultaneously. She pulls Stan's gun on him, preparing to shoot his leg, but ends up shooting the one who didn't apologize, who was actually Bill, who is taken aboard a helicopter and told that his leg can't be saved.
In "Pulling Double Booty", Hayley meets Bill after going to the CIA to have an argument with Stan. Mistaking Bill for Stan, she apologizes which leads to them getting into a relationship. When Stan shows Bill how "Hot" Francine is, Bill tries to have sex with Francine by impersonating Stan. Enraged at Bill trying to hit on Francine, Stan throws Bill out of the window and tells Bill that he cannot see Hayley again. In order to stop Hayley going on a rampage when Bill dumps her, Stan pretends to be Bill to take Hayley out on a date.
Bill, like his double Stan, is voiced by Seth MacFarlane.