Acting for Two: In one episode David meets his exact double, a mobster named Mike Cassidy. In another episode Lou Ferrigno (in his first speaking role) plays a bodybuilder in addition to being the Hulk. The two meet during the climax of the episode.
Executive Meddling: Bruce Banner's name was changed to David because Kenneth Johnson did not want the main character to have what he regarded as a "stereotypically comic-booky alliterative name", although Lou Ferrigno claims that CBS thought the name "Bruce" sounded "too gay." Imagine Kenneth's surprise when it was pointed out to him that his lead actor was called Bill Bixby.
Kenneth had also wanted to change the Hulk's skin color itself from green to red, believing red was more symbolic as "the color of rage". However, Marvel vetoed this idea, stating the Hulk's green skin was an iconic image and could not be changed.
The Other Marty: Richard Kiel (Jaws from The Spy Who Loved Me and Moonraker) was originally cast as the Hulk but the producers decided he didn't have the right body type. There is one blink-and-you-miss-it moment in the pilot where Kiel is playing the Hulk instead of Lou Ferrigno.
Both Richard Kiel and Arnold Schwarzenegger had been considered for the role of the Hulk- Arnie was turned down for being too short, and while Kiel had the job initially and even filmed a few scenes, it was also decided that he was too small (in his muscles, at least) and was replaced. Kiel writes in his autobiography that this was definitely for the best, as his being blind in one eye caused problems with the contact lenses and even resulted in a hair-raising partial loss of vision while he was driving home from the shoot.
Shortly after the series ended, Bill Bixby wanted to do a crossover film with The Amazing Spider-Man (1978), and Bixby even had Nicholas Hammond (Spidey's actor) onboard and ready to go, but Universal Pictures passed. Their claim was that Lou Ferrigno was unavailable, though Ferrigno would later reveal that he'd never even been contacted nor had he even heard of the proposal until 2003.
Ironically, had Bixby not died, a fourth made-for-TV movie would have seen Banner resurrected, and with the ability to control his Hulk power, according to The Other Wiki. Apparently dying didn't exactly cure him. It just would have made it so that Banner could control himself when he transformed... that and actually talk, something the Hulk really didn't do outside of the two-part episode "Prometheus" when Banner was trapped halfway between human and Hulk. Another movie that would have been a backdoor pilot for Iron Man was also being considered, and a She-Hulk movie was in pre-production at one point as well.
You Look Familiar: Several times, most notably Gerald McRaney, who showed up in four episodes as different characters.
Executive Meddling: According to Dick Sebast, the show's creative team spent the first season constantly fighting against this. Then in the second season, there are certain changes behind-the-scenes—leading to the show losing serialization, becoming Lighter and Softer, and seeing attempts to make the characters look trendy. As Sebast said, "What happened to season 2? The network got its way."
Neal McDonough as Bruce Banner and Lou Ferringo as the green Hulk are this, as both roles were voiced by Ron Perlman in their guest appearances on Fantastic Four and Iron Man. Regarding the guest appearance on the former, Luke Perry also replaced Benny Grant as Rick Jones.
California Doubling: Although the final scenes are set in Manhattan (Harlem to be exact), they were shot in Toronto, with the initial showdown between the Hulk and the Abomination being filmed on Yonge Street. Several Toronto icons are visible, most notably the "spinning disc" sign for Sam the Record Man, and the marquee of the Zanzibar Tavern.
Cast the Expert: Rickson Gracie is one of the pioneers of MMA and an 8th-degree black belt in Brazilian Jiu Jitsu. He teaches Bruce some meditation techniques, and presumably some of the moves he uses on the thugs from the factory.
Directed By Castmember: In addition to doing rewrites, Edward Norton actually directed himself in some of his own scenes too, such as the campus scenes, to save time when the director was busy working with 2nd-unit.
Fake Nationality: The cast used a few non-Brazilian actors to play Brazilian characters (the factory owner and the leader of the bully trio). Their attempts to speak Portuguese sound ridiculous to real Brazilians.
Missing Trailer Scene: A scene where a futile Bruce Banner arrives at the Arctic to commit suicide was featured in the trailer, but was deemed too sensitive for young viewers and was removed from the film.
Remake Cameo: Like with the 2003 movie, Lou Ferrigno plays a security guard (this time interacting with Bruce Banner himself). And in a variant, a clip of Bill Bixby (a scene from The Courtship of Eddie's Father) is featured at a certain point to feature both protagonists of the old show.
Role Reprisal: While Lou Ferrigno, the actor that played the Hulk on television, doesn't do the motion-capture for the character in this movie, he lends his voice to the movie version of the character.
Screwed by the Lawyers/Stillborn Franchise: The Hulk has the dubious distinction of being the one hero with his own solo movie that was introduced in Phase One.....and not given a sequel in Phase Two and Three. All subsequent appearances of the Hulk have been in the Avengers movies and Thor: Ragnarok. Part of the reason for this is that Universal still has the distribution rights to the character's solo films so Disney/Marvel Studios can only put him into the Avengers movies.
Wag the Director: Edward Norton rewrote the script himself to bring the film closer in line to the comics. In certain posters, he was credited under the pseudonym of 'Edward Harrison'. Norton's writing credit was later denied by the WGA, and Zak Penn is the only writer credited.
Louis Leterrier originally wanted to cast Mark Ruffalo as Bruce Banner in this movie. Ruffalo would later take over the role after Edward Norton dropped out. David Duchovny was another early candidate.
Ray Stevenson was considered for Emil Blonsky. He would later play Volstagg in the Thor films.
Michael K. Williams' cameo was going to be much longer. He would have pleaded with the Hulk and Abomination to stop their fighting, only to change his mind and basically tell the Hulk, "You know what, never mind, waste this bitch."
Rick Jones was present in early drafts of the film, but ended up being removed once Norton rewrote the script.
Norton's wife Shauna Robertson produced Knocked Up and he wished to have one of the stars appear in a cameo as a computer nerd. The role was offered to Jason Segel, Jonah Hill, and Seth Rogen before Martin Starr was eventually cast.