Mario goes to the store to get some chips, leaving Luigi home alone.
When Mario finds out Peach has a hot new boyfriend, he tries to get back into shape to make himself more attractive for Peach.
When Luigi tries to fix the electrical chords in the storm, he gets struck by lightning. Mario and the others all think he's dead, but Luigi is well alive, and he decides to haunt them by pretending to be a ghost.
When Mario eats Luigi's last special cookie, Luigi beats up Mario, and accidentally puts him into amnesia. Now it's up to Luigi and the rest of the gang to get Mario's memory back.
When Luigi finds out that there are no Luigi Oddysey games and only Mario ones, he decides to make his hat into a hat with googly eyes like in the game. But after he goes to sleep, the hat takes on its own life.
When Mario throws a birthday party for Luigi and someone pops a balloon, Luigi develops a fear of balloons, and Mario and the gang have to find a way to make Luigi get over his fear.