Giant Vampire Bats are creatures portrayed in 3. They have a ten foot wingspan, which makes them larger than the average human, which is six feet. The Latin name for the common vampire bat, Desmodus rotundus, is written beneath a sketch of one which might be the Giant Vampire Bat's scientific name also or be Desmodus rotundus gigantis. For some reason, there is a game of tic-tac-toe on the page possibly just having a little fun or calculating something else. There is one seen behind Grunkle Stan in the opening when they're gathered around the campfire during the theme song.
They seem to resemble a very large Common Vampire Bat. Besides the size, the only real difference is the large, hairy mohawk, which other vampire bats lack.