The Grim Adventures of the KND (2007 TV Short)
When detained, Mandy says the famous "And I would have gotten away with it too, if it weren't for you meddling kids" line.
Dexter, Dee Dee, and Mandark are assimilated into the Delightful Reaper
After calling for the Powerpuff Girls to show up, Billy sees Numbuh 1 from Codename: Kids Next Door came instead and says, "Hey, you're not the Powerpuff Girls." Later, the Powerpuff Girls are seen flying out of the Delightful Reaper, implying they somehow were assimilated without defeating it.
The characters Ed, Double D, and Eddy appear in a small crossover during the end credits entitled Ed, Edd n Mandy where Mandy is chasing after the Eds.
Fred Fredburger says "I also enjoy shows about imaginary friends."
Fred Fredburger says "I also enjoy shows about monkeys going to camp."
Fred Fredburger says "I enjoy shows about monkeys." Adam Lyon also gets assimilated into the Delightful Reaper.
Andy Johnson is one of those seen flying out of the Delightful Reaper at the end.
"The Grim Adventures of the Kids Next Door", a crossover between Codename: Kids Next Door (2002) and The Grim Adventures of Billy & Mandy (2001), is #4.
"Samurai Mac" card in the credits
"Evil Camp Carne" card in the credits
"Class of Numbah 3000" card in the credits