Flappers are the only type of Enemies that has the ability to fly.
To defeat them you must use the Jump attack. If you're already in the air, you can move sideways towards Flappers to defeat them.
Flappers often fly in groups, which is extremely helpful to make great Hit Combos.
You can also have an extra jump when the flying Goons are killed in the air.
After summoning some of the Pets, you will be able to shoot Flappers with different types of projectiles. Some of them will inflict damage to multiple Enemies.