Marvel's Jessica Jones introduces the titular character into the Marvel Cinematic Universe, along with Luke Cage, who'll have his own series next year. But as always with comic-book film and television adaptations, there are plenty of other heroes and villains hiding in plain sight on Jessica Jones. There are also characters with wildly different backstories than the ones we see onscreen, starting with our heroine, Jessica, who actually tried out the masked-avenger thing in the comics before she ultimately became a private investigator ...
Jessica Jones, a.k.a. Jewel, a.k.a. the Knightress
In Jessica Jones, our heroine is already a private investigator when we meet her. During a flashback in episode five, "AKA The Sandwich Saved Me," Jessica's best friend, Trish Walker, suggests a costume for her and the identity of Jewel if she's going to be fighting crime in New York City. "Jewel is a stripper's name, a really slutty stripper," Jessica scoffs. This is actually a nod to Jessica's true origin, as it was told in Alias, the comic series Jessica originated in.
In comic-book canon, the car crash that kills Jessica's family also gives her superhuman strength due to a collision with radioactive materials. As a classmate of Peter Parker's, she witnesses him as Spider-Man fighting the villain the Sandman and becomes inspired to fight crime. (Jessica Jones wasn't written until 2001, so her being present for this fight in 1963's Amazing Spider-Man No. 4 was a backstory given to her by creator Brian Michael Bendis.) Jessica dons a costume and tries becoming a superhero named Jewel, but she runs afoul of Kilgrave and he brainwashes her into killing his archnemesis, Daredevil. She accidentally attacks the Scarlet Witch instead (she wears red just like Daredevil) and the Avengers retaliate, beating Jessica into a coma. After being awoken from the coma by mutant Jean Grey (of the X-Men) when the misunderstanding was realized, Jessica gave up being a superhero save for the final issue, where she briefly goes by the Knightress to take on another Daredevil villain, the Owl. When she gave up being a superhero for good, she opened a private-detective agency.
Kilgrave, a.k.a. Purple Man
Zebediah Killgrave was a physician who became a spy. During a mission, he was affected by a chemical that turned his entire body purple and gave him the power to control minds. He becomes a supervillain and begins to rob banks and build a criminal empire, until he runs afoul of Daredevil. Daredevil's mind is strong enough to overcome the Purple Man's mind-control powers, so he's able to defeat him.
When Purple Man meets Jessica Jones, he becomes enamored with her and puts her under his control for eight months. Annoyed at a newspaper story about Daredevil saving New York City again, Purple Man sends Jessica to kill him. From that point on, his comic-book nemeses are mainly Jessica and Luke Cage.
His backstory is changed on Jessica Jones to create a more realistic depicition of how his powers affect the people around him. It also strips him of his purple skin. (He still has his fancy purple outfits, however.)
Trish Walker, a.k.a. Patsy Walker, a.k.a. Hellcat
Trish's background in the comics starts well before Marvel Comics ever existed — founded in 1939, Timely Comics would eventually become Marvel Comics in the '60s. Before that, Patsy Walker debuted in 1944's Miss America Magazine No. 2. She starred in teen-romance comics throughout the '40s and became a career woman in the '60s.
In 1965, Patsy appears in Fantastic Four and is established as an existing character in the Marvel universe. In 1972, she was reintroduced as the superhero Cat. Disliking the name, Avengers writer Steve Engleheart renamed her Hellcat, and she joins the Avengers. The Patsy Walker era is then retconned as fictionalized comics created by Patsy's mother, Dorothy, about her daughter's childhood.
This translates to Jessica Jones, where Trish's Patsy Walker days are a television series and comic book created by her mother. A fan even runs into Trish and tells her he "misses the red hair." On the show, Trish takes martial-arts training to defend herself against Kilgrave and other assailants; in the comics, she's a martial artist with psychic abilities. So when the hell do we get to see Trish suit up as a superhero? There's a seemingly hidden-in-plain sight reference where Trish appears to have the word "Hellcat" tattooed on her right wrist:
Will Simpson, a.k.a. Nuke
In the comics, Will's name is Frank. He's hired by the Kingpin in 1986's Dardevil No. 232 to kill the superhero. Nuke takes three different colored pills to maintain superhuman strength and abilities. Red for adrenaline, blue to remind his lungs to breathe after he's taken a red, and white to balance him out when he's on neither. Daredevil battles him, but it's ultimately a military chopper that "takes out" Nuke.
Nuke resurfaces later, and his origins are revealed as being part of the Weapons Plus program, which created Captain America and Wolverine. It's highly unlikely Will Simpson will be involved in any Avengers stories, but the probability that he'll return in Jessica Jones or Daredevil as Nuke with an American flag painted on his face is pretty high.
Jeri Hogarth, a.k.a. Jeryn Hogarth
Carrie-Anne Moss plays Jeri Hogarth, who is Jeryn Hogarth in the comics, a character first introduced in Iron Fist. He was a friend of the superhero Iron Fist's father (Iron Fist's Netflix series will debut following Luke Cage's, and before Luke, Iron Fist, Daredevil, and Jessica Jones all join Netflix's The Defenders) and became the lawyer of Heroes for Hire. In the comics, Jeryn is not at all the amoral badass that Jeri is. It's the comics' loss.
Luke Cage: Hero for Hire
Luke Cage was Marvel's attempt to cash in on the blaxploitation craze of the '70s. When Luke's friend Stryker (later the villain Diamondback) wants to steal his girlfriend, Stryker plants drugs in Luke's apartment and gets him sent to prison. There, he's experimented on (in a Super Soldier project, à la Captain America) and gains indestructible skin and super strength. When Luke is released from prison, he uses his newfound abilities to make money, which is the premise of his first comic series, Luke Cage: Hero for Hire.
Luke will have his own series on Netflix in 2016. His backstory has yet to be explained on Jessica Jones, so there's a high possibility this could remain intact.
Reva Connors, Luke's deceased wife on the series, was his girlfriend in the comics. (She's the woman Stryker wanted to steal from Luke.) When Stryker frames Luke by planting drugs in his apartment, the real owners of the drugs come looking for Luke and kill Reva instead.
Rewriting Reva's death to involve Jessica and Kilgrave adds more weight to her as a character, and Jessica and Luke's development as heroes in Jessica Jones.