Grim Poppet, Clever Impersonator, and Hapatra, Vizier of Poisons

Prerequisites

• Grim Poppet on the battlefield
• Clever Impersonator on the battlefield
• Hapatra, Vizier of Poisons on the battlefield

Steps

1. Activate Grim Poppet by removing a -1/-1 counter from it, putting a -1/-1 counter on Clever Impersonator
2. Hapatra triggers, creating a creature token
3. Activate Clever Impersonator by removing a -1/-1 counter from it, putting a -1/-1 counter on Grim Poppet
4. Hapatra triggers, creating a creature token
5. Repeat

Results

• Infinite ETB
• Infinite creature tokens