Hatchery Sliver + Ornithopter + Maskwood Nexus

Steps

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