Which Paper Mario game introduced the Sticker battle system?

Paper Mario: Sticker Star introduced the Sticker battle system. Released for the Nintendo 3DS in 2012, it changed combat by making Mario's attacks depend on collectible, single-use stickers.

Players find, buy, or receive stickers throughout the Mushroom Kingdom and place them in a limited inventory. A Jump sticker can make Mario jump on an enemy, while Hammer stickers provide a different attack. Stickers disappear after use, so battles involve choosing when to spend attacks and finding replacements in the environment.

The system also connects combat with exploration. Special Thing Stickers, based on objects such as scissors or a fan, can solve puzzles and affect boss encounters. Sticker Star was the fourth Paper Mario game and followed Super Paper Mario, which used a more action-oriented platforming format. Paper Mario: Color Splash later expanded the card-and-sticker-inspired approach, while Paper Mario: The Origami King introduced ring-based battles instead. Thus, Sticker Star—not Color Splash or The Origami King—is the series entry that first introduced sticker-based battles.