In the flashback to when the Hulk was created, Bruce Banner briefly turns into the Grey Hulk before turning into the familiar green one. This is homage to "The Incredible Hulk" (vol. 1) #1, the first comic book appearance the Hulk and he was colored grey.
There is a shot of the Hulk's skull during the dream and later a lighted "DANGER" sign flashes. Also when Dr. Banner transforms into the Hulk, the iris of his eyes turn bright green. All of this alludes to the opening title sequence of "The Incredible Hulk (1978)," a live-action TV series which was the first to feature Lou Ferrigno as the Hulk. Ferrigno also provides the voice for the Hulk on this animated series.
The opening scene is an allusion to the Christian story of Adam and Eve. Bruce and Betty are Adam and Eve respectively. Betty, like Eve, grabbed the apple and offered it to the man. General Ross could be seen as God, angry that they took the apple and throwing them out of the garden of paradise.
The Return of the Beast," a two-part opener that sets up the first season's story arc and tells the Hulk's origin in flashback mode. Instead of a gamma bomb that explodes to turn him into the Hulk, Banner is working on a gamma reactor, eliminating the antiquated Cold War elements of the comics' origin and staying in line with the script to the live-action Hulk (2003) film Universal had in development.
Betty Ross is the first character seen both in the dream and in reality.