Evil Twin, and Felidar Guardian

Prerequisites

• Evil Twin in hand
• Felidar Guardian on the battlefield

Steps

1. Cast Evil Twin by paying its mana cost, choosing to have it enter the battlefield as a copy of Felidar Guardian When Evil Twin enters the battlefield, it triggers, blinking Felidar Guardian
2. When Felidar Guardian enters the battlefield, it triggers, blinking Evil Twin
3. Choose to have Evil Twin enter the battlefield as a copy of Felidar Guardian
4. Repeat from step 2

Results

• Infinite LTB
• Infinite ETB