Zoo Escapees is a common Creature — Boar Rhino card from Teenage Mutant Ninja Turtles (TMT), collector number 138. Current market price: $0.11 (foil $0.14), TCGplayer market prices via Scryfall.
When this creature leaves the battlefield, create a Mutagen token. (It's an artifact with "{1}, {T}, Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")