Wee Champion is a common Creature — Minotaur Child Guest card from Unfinity (UNF), collector number 127. Current market price: $0.04 (foil $0.18), TCGplayer market prices via Scryfall.
Whenever you place a sticker, this creature gets +1/+1 until end of turn. If it's an art sticker, instead put a +1/+1 counter on this creature.