Skeleton

Skeletons are aggressive creatures who only appear in the Halloween-themed Supernatural Yard. They are the first new zombie encountered. They always appear in an ambush or as Dynamic Difficulty zombies.

Plants vs. Zombies 2
The Skeleton is the first Supernatural Yard enemy encountered. It is encountered in Night 1's Skeleton Army! ambush in small quantities and is a common sight after.

Suburban Almanac entry
Skeleton

TOUGHNESS: Fragile SPEED: Flighty

Rush into the lawn in an army and punch plants into oblivion.

Despite the fact that I'm not a zombie, I love braaains anyway. Don't ask.

Plants vs. Zombies 2

 * Any level with Skeleton Army!
 * Any Supernatural Yard level if your Dynamic Difficulty is high enough

Plants vs. Zombies 2
Skeletons attack twice as fast as Zombies but do half the damage. They are as fast as a Zombie Chicken. Multiple Skeletons can be affected by the same pea/plasma ball etc... Keep this in mind. Set up something like Force Field Infi-nut or a lane of Endurian for every level. Note that they will not trigger plants that must be eaten to do something because they punch plants. They can devastate defenses early in the levels and that is often when they start. A splash plant like Wintermelon can deal with them all at the same time.

Trivia

 * Skeletons are the first enemy to not be a zombie.