One day, Gay Luigi wouldn't stop talking about spaghetti. This annoyed Fat Mario, who tried to shut Gay Luigi up by nailing him to a cross. Miraculously, Gay Luigi survived this experience, and some people who heard this story started to believe that Gay Luigi was the fourth Messiah, after Abraham, Jesus, and Mohammed.
Luigiism is similar to Christianity, but with the treatment of homosexuality and heterosexuality reversed and with Gay Luigi taking the place of Jesus. According to Luigiist doctrine, Gay Luigi also plays a slightly different role than Jesus, condemning certain people to hell instead of allowing certain people to go to heaven. Spaghetti is also substituted for bread in their version of communion.