They have slow movement speed, extremely low health and many similarities to Those Guys. Due to them not attacking, this enemy will never deal any damage; they simply sit in front of their target (and never stop shooting those pretty fireworks).
This enemy doesn't attack and has the lowest health possible. Nearly anything can kill them, so either use them to the benefit Long Distance Cats or just ignore them outright.
There is actually one scenario in which they'll attack: when they spawn as a boss with a unit already inside their range, such as in Joy & Prosperity 2022. The attack animation consists of them launching three fireworks into the sky in quick succession. They won't attack again after that.
Firework Guys 1 and Firework Guys 2 are the only enemies in the game that don't normally attack.
They have the second-shortest range in the game, beaten by only One Horn.