Repel Gel

Repel Gels are rare items found in Paper Mario. The gel makes Mario Invisible for three turns. They are dropped by ? Mark Li'l Oinks and 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 Question Block in Gusty Gulch, and by paying Rip Cheato 64 coins for the fourth time.

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