According to Tim Roth, Edward Norton re-wrote scenes every day. Norton and Liv Tyler also spent hours discussing their characters' lives (especially before the Hulk appeared).
Paul Soles, who portrays "Stanley Lieber", the owner of the pizza shop, provided the voice for Bruce Banner/The Hulk in the Hulk (1966) animated series and later went on to provide the voice of Spider-Man/Peter Parker in Spider-Man (1967). The character's name is another tribute to Hulk co-creator Stan Lee. Stan Lee's birth name was Stanley Lieber.
Captain America: Civil War (2016) is the first reappearance of William Hurt as General Thaddeus Ross since this Captain America: Civil War, an eight-year absence for his character. The Russo brothers, directing that film, wanted to incorporate Ross, as they felt that character had been forgotten a bit since this film.
Tim Roth was supposed to return as Abomination in Avengers: Age of Ultron (2015), but the character was cut. Roth finally reprised the role in Shang-Chi and the Legend of the Ten Rings (2021) and She-Hulk: Attorney at Law (2022).
Michael Kenneth Williams: As a bystander in Harlem. Edward Norton wrote the part specifically for him, because he was a big fan of Williams' work on The Wire (2002).
Stan Lee: (at around 13 mins) the comic writer who co-created The Incredible Hulk in 1962 is the man who drinks the soft drink contaminated with Bruce Banner's blood.
Rickson Gracie: (at around 5 mins) appears as the Jiu-Jitsu instructor that is teaching Bruce Banner breathing exercises.
Paul Soles: As pizzeria owner Stanley Lieber. Soles voiced the Hulk in The Marvel Super Heroes (1966) and Hulk (1966). His character's name is a reference to the real name of Hulk co-creator Stan Lee.