Splinter, Radical Rat is a rare Legendary Creature — Mutant Ninja Rat card from Teenage Mutant Ninja Turtles (TMT), collector number 251. Current market price: $1.58 (foil $2.31), TCGplayer market prices via Scryfall.
If a triggered ability of a Ninja creature you control triggers, that ability triggers an additional time. {1}{U}: Target Ninja can't be blocked this turn.