Stamp

Stamps are collectables found in many Wii U games. They are earned by completing certain tasks ingame, and can be used on handwritten Miiverse posts.

Super Mario 3D World
Stamps first appeared in Super Mario 3D World. There are 85 stamps in this game. 80 of them are scattered in levels or Sprixie Houses, while the other 5 are gained by completing every course with any character (1 gained per character).

NES Remix
Stamps make their second appearance in NES Remix, where there are 100 Stamps in it. They are gained by obtaining enough Bits. 10 are unlocked from the start, while 90 must be unlocked.

NES Remix 2
In the sequel NES Remix 2 they appear once more, and like in the prequel, there are 100 Stamps, but none of them is unlocked from the start. 95 of them are earned by obtaining Bits, while the other 5 are unlocked by completing certaing challenges.

Captain Toad: Treasure Tracker
Stamps are set to appear in Captain Toad: Treasure Tracker, working like in Super Mario 3D World.

Mario vs. Donkey Kong (Wii U)
Stamps are set to appear in Mario vs. Donkey Kong (Wii U).