Mighty Mutanimals + Hapatra, Vizier of Poisons + Barrenton Medic

Mighty Mutanimals

Hapatra, Vizier of Poisons

Barrenton Medic

How it works

1. Activate Barrenton Medic's first ability by tapping it.
2. Activate Barrenton Medic's second ability by putting a -1/-1 counter on it.
3. Hapatra triggers, creating a creature token.
4. When the creature token enters, Mighty Mutanimals triggers, putting a +1/+1 counter on Barrenton Medic.
5. Resolve the Barrenton Medic ability from step 2, untapping it.
6. Repeat.