The Eye-Bats are race of strange creatures in Gravity Falls.
When Ford went to live in Gravity Falls to find out more about the supernatural phenomena there, the Eye-Bats were among the creatures he discovered. He managed to find some, capture them, put them in a jar and wrote about them in Journal 3. In the same flashback, one of the Eye-Bats is also pinned on the wall in Ford's room.
An Eye-Bat is seen at the end of Ford's dream in the nightmare realm in "The Last Mabelcorn," near the Zodiac.
In "Weirdmageddon Part 1", swarms of larger forms of red-winged Eye-Bats are seen coming out of the Nightmare realm with Bill Cipher and serve as Bill's henchmen.
Continued in "Weirdmageddon 2: Escape From Reality", the giant Eye-Bats are still flying around Gravity Falls, turning people into stone and bringing them to Bill.
In "Weirdmageddon 3: Take Back The Falls", the red-winged Eye-Bats are still flying around Gravity Falls, one near the Mystery Shack before turning a nearby raccoon to stone. They are later seen among Bill's henchmen who battle against the Shacktron Old Man McGucket built, several being controlled by Paci-Fire. After the demons had been sucked back through the rift, the Eye-Bats are seen still living in Gravity Falls, with a few being scared away from inside a barn by Sprott.
The Eye-Bats look like eyeballs with yellow pupils and bat-like wings at the sides. They appear to be bioluminescent, as their bodies emit light.
The ones from the Nightmare Realm appear larger than the ones Ford encountered. Their wings also appear different, being more bat-like than their smaller counterparts.