Stillwell first appeared in The Amazing Spider-Man #20 (January 1965), and was created by writer Stan Lee and artist Steve Ditko.

When Jameson saw an article about inducing animal mutations into humans, he visited the scientist that established this experiment: Dr. Farley Stillwell.

However, Stillwell learns that the process will eventually drive Gargan insane and unsuccessfully attempts to cure him, during which he falls to his death.

In addition, their mother is Melodia Stillwell, who is also known as Madame Monstrosity and similarly specializes in combining animal and human DNA.

[1] An alternate universe variant of Farley Stillwell from Earth-58163 appears in House of M: Avengers #1 as one of the scientists who gave Luke Cage his powers.