Kukulkan's species were a race of intelligent, space-faring, winged serpents. Their wings and tails were feathered and they possessed a feathered mane at the base of their skulls that was in turn adorned with a single backward-curving horn.

Kukulkan's species fell into near extinction some time before Humans gained the ability to control fire on Earth, leaving Kukulkan himself as the only survivor. (TAS: "How Sharper Than a Serpent's Tooth")