The Jolly Balloon Man + Ertha Jo, Frontier Mentor + Pestermite

The Jolly Balloon Man

Ertha Jo, Frontier Mentor

Pestermite

How it works

1. Activate a mana-producing creature by tapping it, adding at least 1.
2. Activate The Jolly Balloon Man by paying 1 and tapping it, targeting the mana-producing creature.
3. Ertha Jo triggers, copying The Jolly Balloon Man's ability, targeting Pestermite.
4. Resolve the copy of The Jolly Balloon Man's ability, creating a token copy of Pestermite that is a 1/1 Balloon with haste.
5. When Pestermite enters the battlefield, it triggers, untapping The Jolly Balloon Man.
6. Resolve the Jolly Ballon Man ability from step 2, creating a token copy of the mana-producing creature that is a 1/1 Balloon with haste.
7. Activate the mana-producing creature token by tapping it, adding at least 1.
8. Repeat from step 2.

This engine relies on Ertha Jo, Frontier Mentor's passive ability to duplicate targeted activated abilities whenever you use them. By pointing The Jolly Balloon Man's tapping activation at a mana producer, Ertha Jo lets you copy that creation effect to target Pestermite instead. As the resulting token copy of Pestermite enters the battlefield, its triggered ability untaps The Jolly Balloon Man so you can repeat the process indefinitely, while also spinning off an army of hasty token copies along the way.