Sakashima the Impostor + Felidar Guardian

Prerequisites

You have enough mana to cast Sakashima the Impostor.

Steps

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