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.
In the first few episodes, the production uses colored light to great effect to separate out each individual Defender story. Each scene involving Daredevil has a hint of red. Jessica Jones is lit with purple. Iron Fist with green and Luke Cage is lit in shades of yellow. As the series progresses and the Defenders become aligned, the four colors eventually turn into more neutral whites and blues.
In the Marvel Comics, the Defenders have a constantly shifting roster. As of 2016, the Marvel Comic Universe has eighteen 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 last shot of Danny Rand features him crouched on a rooftop overlooking the city, apparently fulfilling Daredevil's request to keep his city safe. In the comics, Danny became Daredevil to help fool the world after Matt's secret identity was outed.
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.
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.
As of this series, Captain America and Iron Man are the only Avengers referred to by name (Captain America in Daredevil (2015) season one, Tony Stark in season one of Luke Cage (2016)). 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 (2015).
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.
Throughout the series Danny Rand/Iron Fist (Finn Jones) Luke Cage (Mike Colter), and Matt Murdock (Charlie Cox) all wear the colors of their respective character. Iron Fist wears something of green clothing, Daredevil wears something red, and Luke Cage wears something with yellow in it.
Contains the largest amount of series regulars out of any of the Marvel Netflix series. All previous shows have had thirteen episode seasons while the Defenders is the shortest at eight episodes. This was the case as production had to begin on the second seasons of Jessica Jones (2015) and Luke Cage (2016).
There's a "sly" easter egg from the anime series called Bleach shown in the third episode where Alexandra takes Elektra to a room filled with weaponry. As Elektra sorts through her master's swords, there's one shot which shows Renji Aburai's iconic Zanpakuto shelved behind Elektra. His Zanpakuto is a spiked sword known as Zabimaru and is one of the franchise's most famous blades. The Zanpakuto has an odd Shikai state that gives it jagged edges. The segmented blade can be used as both a rigid sword or whip. Although this easter egg doesn't mean Bleach has tied to the Marvel Cinematic Universe, it just so happens that the show brought it as a set prop.
Sigourney Weaver was earlier going play a comic book supervillain; 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.
Rosario Dawson (Claire Temple) and Mike Colter (Luke Cage) appeared in the Men in Black film franchise, Rosario Dawson played Laura Vasquez in Men in Black II (2002), and Mike Colter played the Colonel in Men in Black 3 (2012).
Alexandra (Sigourney Weaver), Madame Gao (Wai Ching Ho), Sowande (Babs Olusanmokun), Murakami (Yutaka Takeuchi), and Bakuto (Ramon Rodriguez) are the "Five fingers of The Hand". Madame Gao first appeared in Daredevil (2015) and Bakuto first appeared in Iron Fist (2017).