Total Drama/The Grim Adventures of Billy and Mandy

Cast

 * Ezekiel as Billy
 * Crimson as Mandy (They're both described scary)
 * Rodney as Grim (They both are kind-hearted)
 * Cameron as Irwin (They're both African-American and wear glasses)
 * Owen as Harold
 * Izzy as Gladys (They both have orange hair)
 * Chris as Hoss Delgado
 * Amy as Eris (They both have blonde hair)
 * Bridgette as Claire (They both have ponytails)
 * Geoff as Phillip
 * Leonard as Nigel Planter
 * Cody as Nergal
 * Harold as Nergal Jr. (They both wear glasses)
 * Max as Sperg
 * DJ as Melvin
 * Scarlett as Mindy (They both have red hair)
 * Chef as Lionel Van Helsing
 * Beth as Aunt Sis (They both wear glasses)
 * Trent as Lord Pain
 * Duncan as Creeper
 * Heather as Malaria (They both have black hair)
 * Scott as Boogie Man
 * Justin as Lord Moldybutt
 * Gir (from Invader Zim) as Fred Fredburger