The Jolly Balloon Man in exile (exiled by Agatha's Soul Cauldron).
All other permanents on the battlefield.
Midnight Guard has at least one +1/+1 counter on it.
Midnight Guard does not have summoning sickness.
You control at least one additional nonlegendary creature.
({1} magic symbol) available.
Steps
Activate Midnight Guard using The Jolly Balloon Man's ability by paying ({1} magic symbol) and tapping it, creating a token copy of another nonlegendary creature you control that is a 1/1 Balloon with flying and haste in addition to its other types.
When the creature token enters the battlefield, Midnight Guard and Mana Echoes trigger.
Resolve the Midnight Guard trigger, untapping it.
Resolve the Mana Echoes trigger, adding ({C} magic symbol) for each creature you control that shares a creature type with the creature token.
Repeat.
Results
Infinite LTB.
Infinite ETB.
Infinite sacrifice triggers.
Infinite death triggers.
Infinite colorless mana.
Infinite creature tokens with haste.
Infinite token copies of each creature you control with haste except Midnight Guard.