Cathars' Crusade, Animation Module, and Crystalline Crawler

Prerequisites

• Cathars' Crusade on the battlefield
• Animation Module on the battlefield
• Crystalline Crawler on the battlefield
• Crystalline Crawler does not have summoning sickness

Steps

1. Activate Crystalline Crawler's second ability by tapping it, putting a +1/+1 counter on itself
2. Animation Module triggers, holding priority, activate Crystalline Crawler's first ability by removing a +1/+1 counter from it, adding
3. Resolve the Animation Module trigger, causing you to pay to create a 1/1 Servo artifact creature token
4. The Servo enters the battlefield, triggering Cathars' Crusade, putting a +1/+1 counter on each creature you control
5. Animation Module triggers once for each creature you control
6. Resolve all but one Animation Module trigger, choosing not to pay
7. Activate Crystalline Crawler's first ability by removing a +1/+1 counter from it, adding
8. Repeat from step 3

Results

• Infinite creature tokens
• Infinite ETB
• Infinite +1/+1 counters