This is the second Sylvester Stallone film in which one of the bad guys is called Cyrus. The first was Get Carter (2000).
In Cyrus's warehouse the arcade game Robocop can be seen. A parallel movie where the city is in chaos and anarchy looking for a beacon of hope.
When Sam is injured in the hospital, the PA says, 'Dr. Davis, telephone please. Dr. Davis, telephone please." This is an old hospital sound effect found on a unidentified sound effect album, that is very common in use for background effects. It's also famously found at the beginning of the 1988 album Operation: Mindcrime by Queensrÿche, in the opening of 'T.nT.' by Motley Crue (1989), and 'Catapult' by Phish (1992), as well as being recognized in many other TV shows and movies.
There are a few hints that Joe Smith is in fact Nemesis, not Samaritan. The opening credits sequence focuses on the creation of the hammer used by Nemesis. Even after Sam learns the truth about Joe's power and Joe comes clean with him, Joe continues to state, truthfully, that he is NOT Samaritan. Sam never thought to ask if Joe was Nemesis - Joe simply wouldn't volunteer that information. At several points during his fights with gang members, Joe shows extreme rage before hesitating and then performing a non-lethal attack. This is Joe fighting his villainous urge to kill and instead show restraint as his brother would have.
This is the second time Pilou Asbæk got killed as a villain, Cyrus in both Julius Avery's movies. This and Overlord (2018).
While in the hospital getting Sam's broken arm in a cast there are two calls for doctors "Dr. Blair, Dr. Blair... Dr. Jane Hamilton, Dr. Jane Hamilton" these are used in multiple TV shows and movies also on Queensrÿche's Album "Operation Mindcrime".
When Joe is in the hospital with Joe, a voice over the P.A. says, " Dr. Davis telephone please, Dr..Davis..." Then it says Dr. Blair...this is the exact recording from Mötley Crüe's "Dr. Feelgood".
This is the first time in a film that we get to see Javon 'Wanna' Walton's boxing background put to use.
Even though the final fight scene in the burning building was incredible, there's no way in a blaze of that size that the characters could've seen or breathed do to smoke.
Sylvester Stallone and Martin Starr would later work on Tulsa King (2022) together.
First of two 2021 superhero films to feature Sylvester Stallone. The second film is "Suicide Squad" (with Stallone in a voice role).
The film is inspired by Unbreakable (2000) and Finding Forrester (2000).
This is Pilou Asbæk's first Julius Avery film since Overlord (2018).
Sylvester Stallone, Martin Starr, and Michael Aaron Milligan have made appearances in the MCU. Stallone was in Guardians of the Galaxy Vol. 2 (2017), Starr was in The Incredible Hulk (2008) and the MCU Spider-Man films, and Milligan was Paul Rudd's stand-in for Ant-Man (2015).