The Grim Adventures of Billy and Mandy - Season 3 - Eps 24: Five O'Clock Shadows
Grim is annoyed by Billy who thinks that a shadow is following him. Grim takes Billy and Mandy to the Shadows' World, where their opposites live. Grim tells them to do whatever they want, but to be back at 5 o'clock, when the portal to the normal world opens. Grim also warns Billy about the Door to Other Dimensions, but Billy opens it and a multitude of Billys come out an wreak havoc.
About The Grim Adventures of Billy and Mandy

Title: The Grim Adventures of Billy and Mandy
First Air Date: 2001-08-24
Last Air Date: 2007-11-09
Status: Ended
Rating: 8.045/10 (from 958 votes)
Language: EN
Seasons: 8
Total Episodes: 184
Network: Cartoon Network
Genres: Animation, Comedy, Kids
Production Companies: Cartoon Network Studios
Synopsis
The exploits of the Grim Reaper, who has been forced into being the best friend of two children. A spin-off of the show Grim & Evil.
Cast

Greg Eagles
Grim (voice)

Richard Steven Horvitz
Billy (voice)

Grey DeLisle
Mandy (voice)

Vanessa Marshall
Irwin (voice)