Mighty Mutanimals, Barrenton Medic, and Flourishing Defenses

Prerequisites

• Mighty Mutanimals on the battlefield
• Barrenton Medic on the battlefield
• Flourishing Defenses on the battlefield

Steps

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. Flourishing Defenses 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

Results

• Infinite ETB
• Infinite creature tokens