Billy Jessup is the secondary antagonist of Jumanji. He was an enemy of Alan Parrish when they were kids.
Jessup was hiding behind the statue of Angus Parrish, Alan's ancestor from 1869, the year 2 boys had dug up Jumanji. Jessup then chased after Alan to the shoe factory, and watched as he ran inside. He hates Alan because he keeps hanging out with his girlfriend Sarah Whittle. He and his gang later took Alan's bike when he got out and smashed him in the lip. He was never seen during the rest of the film, although his name was mentioned a lot.
Gary Joseph Thorup played Billy Jessup and was great in the film.