Flappers are the only type of Enemies that can fly.
To defeat them, you must use the Jump attack. If you're already in the air, you can move sideways toward Flappers to defeat them.
Flappers fly in groups, which is extremely helpful in making 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 can shoot Flappers with different projectiles. Some of them will inflict damage to multiple Enemies.