The Hulk was inspired by the story of Dr. Jekyll and Mr. Hyde. In contrast to the quiet Dr. Bruce Banner, the Hulk is as a childlike persona who just wants to be left alone, but is continually forced to battle foes determined to hunt him down. This is somewhat similar to that of Universal Studios' 1931 film Frankenstein, another major influence on the character.
In the first issue of The Incredible Hulk, the Hulk was supposed to be gray. However, the publishers of the time had difficulties with printing a consistent and clear shade of gray, so after the first issue they decided to make him green and that color stuck. For a period later in the series, the Hulk reverted to a gray color.
In the origin story of the Hulk, Dr. Bruce Banner is a military scientist who has developed a new type of weapon called the "Gamma Bomb." As the bomb is being tested (in a fashion reminiscent of the Trinity atomic bomb test), Dr. Banner notices that teenager Rick Jones has driven his car onto the test site. Banner races out into the open to bring the young man to safety, but the bomb explodes before he can reach safety himself. Banner is subjected to an incredible dose of gamma rays, and this is what causes him to transform into the rampaging Hulk. At first he becomes the Hulk when the sun goes down, but soon the more familiar transformation occurs whenever Dr. Banner becomes angry or emotional.
The plots of many of the earliest Hulk stories involve General Thunderbolt Ross continually pursuing the Hulk, his "Hulkbuster" U.S. Army group at his side. Ross's daughter Betty is a love interest for Bruce Banner and often criticizes her father for going after the Hulk so relentlessly without regard to her feelings for the Hulk's alternate identity. General Ross's right-hand-man, Major Glenn Talbot, is also in love with Betty but is an honorable man and is torn between pursuing the Hulk and gaining Betty's love in an honest way. Teenager Rick Jones is the Hulk's first and only friend for a time. Later on, another teenager named Jim Wilson becomes the Hulk's friend.
The Hulk appeared in the premiere run of his own comic book series created by Stan Lee and Jack Kirby during the early 1960's, at the same time as other famous Marvel characters including the Fantastic Four, Thor, and The Avengers. The initial The Incredible Hulk series only ran for six issues before being cancelled by Marvel, due to low sales. However, the character's brief run was popular enough to be noticed by creators Kirby and Lee. Kirby and Lee realized that their character had found an audience in college-age readers -- a demographic that had been entirely ignored by comic books until that time. This inspired them to keep the Hulk alive through numerous guest appearances in other comic books, and by adding him to the ranks of various superhero teams that were making their initial appearances in the Marvel Universe, including The Avengers and The Defenders. The Hulk was then given a regular backup feature in Marvel's ongoing series Tales To Astonish. After several years, the Hulk's popularity was enough to cause the book to be renamed The Incredible Hulk, where its run continued until March 1999.