Hatchery Sliver + Arcane Adaptation + Crimson Kobolds

Hatchery Sliver

Arcane Adaptation

Crimson Kobolds

How it works

1. Cast Crimson Kobolds by paying 0, and choosing to pay its replicate cost an arbitrarily large number of times by paying 0.
2. Crimson Kobolds triggers, creating a copy of it for each time its replicate cost was paid.
3. Resolve all Crimson Kobolds spells, causing the nontoken Crimson Kobolds to enter the battlefield, and creating a token copy of it for each time its replicate cost was paid.