In this series, the founding members of the Defenders are Daredevil, Jessica Jones, Luke Cage and Iron Fist. In the comics the Defenders were formed by the Incredible Hulk, Doctor Strange, Silver Surfer and Namor the Sub-Mariner.
Matt Murdock plays The Defenders' theme song on the piano in episode six, The Defenders: Ashes, Ashes (2017).
In the Marvel Comics, the Defenders have a constantly shifting roster. As of 2016, the Marvel Comic Universe has 18 characters who have appeared in the Defenders: Dr Strange and the Incredible Hulk (who have their own films) Captain America (who has his own series) Yondu, Drax the Destroyer and Howard the Duck (from Guardians of the Galaxy (2014)) Scarlet Witch and the Vision (from Avengers: Age of Ultron (2015)) Hank Pym and Scott Lang (Ant-Man) and Janet van Dyne (Wasp) (from Ant-Man (2015)) Daredevil, Luke Cage, and Iron Fist (who all have their own series) Patsy Walker (Hellcat) (in Jessica Jones (2015)) Valkyrie (from Thor: Ragnarok (2017)) Spider-Man (from Spider-Man: Homecoming (2017)) Carol Danvers (Captain Marvel) (from Captain Marvel (2019))
The IP address hidden in the first teaser trailer leads to a site with information about The Defenders.
When Matt and Jessica are leaving the police station, a photo of Stan Lee can be seen on a wall in the background.
One of the trailers shows black and white security camera footage of the four defenders in an elevator with a time stamp in the top right corner. The time reads, "8:18", in hours and minutes. This is a reference to the release date of August 18th.
Sigourney Weaver was announced to join the series on her 67th birthday. Her character's name is Alexandra, which happens to be her middle name in real life.
The budding friendship between Luke Cage and Danny Rand is a reference to the Heroes for Hire, a small business started by the two in the comics. Both actors have stated their desire to make a Heroes for Hire series.
As of this series, Captain America and Iron Man are the only Avengers referred to by name (Captain America in Daredevil season one, Tony Stark in season one of Luke Cage). All other references were rather subtle such as "an iron suit, or a magic hammer" said by Wesley in Daredevil, and "The big green dude and his crew" by both Luke and Jessica in Jessica Jones.
Contains the largest amount of series regulars out of any of the Marvel Netflix series. All previous shows have had 13 episode seasons while the Defenders is the shortest at 8 episodes. This was the case as production had to begin on the second seasons of Jessica Jones (2015) and Luke Cage (2016).
The names of The Defenders' stars appear based on the release date of their respective character's solo series. The order is as follows. Daredevil played by Charlie Cox, Jessica Jones played by Krysten Ritter, Luke Cage played by Mike Colter and Iron Fist played by Finn Jones.
Rosario Dawson (Claire Temple) and Mike Colter (Luke Cage) have both appeared in the Men In Black Franchise, Rosario Dawson played Laura Vasquez in MIB2, and Mike Colter played the Colonel in MIB3.
Sigourney Weaver was earlier going play a comic book super villain; when director Bryan Singer was involved in the early stages of X-Men: The Last Stand (2006), he had written the role of the main antagonist, Emma Frost, with Weaver in mind. Weaver's character Alexandra has a penchant for wearing all white, very similarly to Emma Frost.
Throughout the series Danny Rand/Ironfist (Finn Jones) Luke Cage (Mike Colter) and Matt Murdock (Charlie Cox) all wear the colors of their respective character. Ironfist wears something of green clothing, Daredevil wears something red, and Luke Cage wears something with yellow in it.
Josie's Bar and its bartender/owner Josie herself, come straight from Daredevil's comics, and they are also quite prominent in the Daredevil (2015) TV series.