Ernest is a bully who commissions sports that involve kids misbehaving (in unambiguously bad ways, rather than resisting oppression by adults, which is a central theme of the series). Ernest is always seen with a lollipop in his mouth and is frequently called "Ernie" by Numbuh 4, a close associate and nemesis of his.
Ernest first appeared in Operation: M.A.T.A.D.O.R., where he holds the "Bully Fights", in which innocent adults are driven mad with caffeine (being tricked into going there by signing up for a "How to be a Better Dad" seminar) and used for Bull Fighting. Numbuh 4 competed in the sport as a matador, which upset his team, as it went against their moral policies and had been interfering with his duties as a KND Operative. In last appearance G.A.R., Garfish bit his arms, face and legs before he got eaten by a giant garfish.