Repel Gel

Repel Gels are rare items in Paper Mario. The gel makes Mario invisible for three turns, causing enemy attacks to go right through him. They can only appear in a few select areas, such as Jr. Troopa's Playground after smashing the Stone Block there after Mario acquires the Super Hammer, in a ? Block in Gusty Gulch, in a hidden block near the shore of Jade Jungle, behind a tree in Shiver Snowfield, and by paying Rip Cheato sixty four coins for the fourth time. They are also dropped by purple question mark Li'l Oinks.

In Paper Mario: The Thousand-Year Door, the Repel Gel is replaced by Boo's Sheet, which is a much more common item.