From the Super Mario Wiki
The Slimy Shroom is an item found in Super Paper Mario. Its surface is covered in a buttery glaze, and it replenishes ten HP and cures poison. It is only obtained by collecting 150 Shop Points or sleeping in the inn in Flopside after choosing the Star package (Mario has to Flip to find it). The Slimy Shroom can be used to create a Slimy Extract.
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