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I Can't Believe It's Not Butter!
From Unmariowiki
I Can't Believe It's Not Butter! is butter made from toads. It first appeared in DEH MARIO BROS. IN DUH HUUD!, where Mario explains I Can't Believe It's Not Butter! when eating Toad. Although not seen in anymore games, it did make a cameo appearance in the Super Mario Bros. Stupid Show!, in the episode BEWARE, Mario is driving to work, when I Can't Believe It's Not Butter! drives by.