Stupid Mario Brothers

It came from Ash's Toilet (1x8)

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Ash gets a letter from Pikachu telling him that Wobbuffet got stuck in the toilet. So he asks Mario and Luigi to plunge it. The duo dance through a grocery store and arrive at Ash's house. Mario and Luigi plunge Wobbuffet and it gets stuck to Mario's face. Eventually, Luigi manages to get Wobbuffet off and they decide to no longer be plumbers and get real jobs, leaving Ash.