The show's existence is largely the result of a viewer poll. An Internet and call-in event called Big Pick was held from August 24 to August 25, 2000. The three final choices were Grim & Evil, Whatever Happened to Robot Jones? and Longhair and Doubledome. Out of the three, Grim & Evil won the most votes. The first season appeared on Cartoon Network in 2001. Robot Jones would later be made into a full series despite losing; Longhair and Doubledome would reappear with another pilot episode in another Big Pick-style show later on, only to fall short once again.

Originally part of Grim & Evil, Billy & Mandy served as the main show. In each episode, an Evil Con Carne short was put between two Grim shorts. On occasion, it was the other way around, with two Evil shorts and one Grim short. In 2003, the network separated the two and gave both a full length show. The short-lived Evil Con Carne show was cancelled once the already-produced season had aired. In 2004, it was given another short-lived run with the newly created intro and end credits, only to be cancelled again. Some characters from Evil Con Carne, usually Skarr (who eventually became Billy's neighbor), occasionally appeared on The Grim Adventures of Billy & Mandy.

According to Maxwell Atoms' blog on MySpace, the show ended post-production in spring 2007, after having 78 full half-hour episodes, which is as many half hours as Cartoon Network has given to any of its original series. It currently airs on Teletoon.

For further information, visit IMDb or http://en.wikipedia.org/wiki/The_Grim_Adventures_of_Billy_&_Mandy Wikipedia].