Raiders of the Lost Pizza is the tenth episode of Regular Show's fifth season. It follows around Mordecai, Rigby and Wally's adventure searching for an ancient pizza.
Mordecai, Rigby and Wally are up to their usual antics, playing Star Wars with Mordecai playing Obi-Wan, Rigby playing Anakin and Wally playing Greedo. Once again, it's "Pizza-Movie Night"! Rigby's got the popcorn, Mordecai's got the soda and pizza, and Wally's got the movie. It's not the other one from the episode, it's 1981's Raiders of the Lost Ark. Wally says he and his grandfather used to watch when Wally visited his fishing cabinet. They watch the movie all night until 12:00 am, when gunshots are firing.
Mordecai, Rigby and Wally find themselves in the Peruvian jungle in 1936, from the movie they were watching. Mordecai finds himself as "Indiana Mordecai Jones", Rigby as "Rigby Ravenwood" and Wally as a new character: "Wally De Quon". As they search the jungle, Mordecai, Rigby and Wally enter an ancient temple. After having many encounters, they stumble upon Indiana Jones and Satipo, almost retrieving a golden idol. As Mordecai, Rigby and Wally enter a pare room, they discover a rare diamond crystal and take it setting, off the traps. They escape with the help of Indiana Jones, but encounter Rene Belloq and his partner, Benson. They're forced to give the treasures and they escape on a waiting seaplane.
Back at the college, the trio and Jones are given a new assignment: Jones is to find the Ark of the Covenant while Mordecai, Rigby and Wally are to find The Pizza of the Covenant. They set off to Nepal to gain help from Indiana Jones' childhood love interest Marion Ravenwood. There they meet her and she refuses to give them what they need: the headpiece for the Staff of Ra.