Agatha's Soul Cauldron, Inquisitive Puppet, and Railway Brawler

Prerequisites

• Agatha's Soul Cauldron on the battlefield
• Inquisitive Puppet in exile
• Railway Brawler on the battlefield

Steps

1. Activate another creature you control that has a +1/+1 counter on it by exiling it, creating a 1/1 Human creature token
2. When the Human enters the battlefield, Railway Brawler triggers, putting a +1/+1 counter on the Human token
3. Repeat using the Human token instead

Results

• Infinite ETB
• Infinite LTB