Lernaean Hydra
The initial idea for "Ghidorah, the Three-Headed Monster" came from Tomoyuki Tanaka, who also created Godzilla. Tanaka's inspiration came from illustration of the Lernaean Hydra in a book about Greek Mythology, and Orochi of Japanese folklore. Tanaka was enamored with the idea of Godzilla fighting a multi-headed serpent, but considered seven or eight heads to be too excessive, and thus the number of heads was reduced to three. The final version was a three-headed dragon with large wings, two tails and of extraterrestrial origin.