Super Mega Ultra Shroom

A Super Mega Ultra Shroom is a Mushroom that was mentioned by Mimi in Super Paper Mario. Based on Mimi's personality, it may be assumed that in actuality is no such mushroom as while it was mentioned Mimi was disguised at Merlee and was offering various things (similar to Hooktail), saying that she'd give it to Mario and his party along with the Pure Heart if they signed a contract for them to pay 10 million Rubees.

This may be identified with at least some falseness, as there were only eight Pure Hearts in existence, two of which Mario already had.

Trivia

 * The name of the mushroom is a combination of Super Shroom, Mega Mushroom, and Ultra Shroom, all but the second of which can be found in the Paper Mario series. Considering it was made up, it may also be a reference to Mimi's favorite TV show, Super Ultra Goomba Bros., another portmanteau of multiple Mushroom prefixes.