Rick and Morty/The Grim Adventures of Billy and Mandy

Version 1

Rick as Grim

Morty as Billy

Summer as Mandy

Version 2

Rick as Mandy

Morty as Billy

Jerry as Irwin

Beth as Grim

Version 3

Rick as Billy

Morty as Mandy (both names start with M and end in Y)

Jerry as Irwin