This is where he killed my father... What I need... I'll find here.
~ Harry Osborn.
Harold Theopolis "Harry" Osborn, also known as the Green Goblin, American Son and Kindred is a major character in Marvel Comics, specifically serving as a supporting character and occasional antagonist towards Spider-Man.
He is the best friend of Peter Parker/Spider-Man, who would later turned to villainy and adapted the Green Goblin persona in an attempt to avenge his father Norman's "death". In later years, however, Harry would come to redeem himself and reject his father's legacy.
Harry Osborn was the son of wealthy industrialist, Norman Osborn, the original Green Goblin. He went to the same college as Peter Parker, aka Spider-Man. They were roommates for a time, during which Harry encountered occasional problems with drugs. When his father died, Harry found the body and removed the costume.
After learning that Peter was Spider-Man he donned his father's costume and proclaimed himself the Green Goblin. After destroying Peter's apartment in a battle with Spider-Man, he began seeing a psychiatrist who tied him up and became himself the Green Goblin.
Harry later suffered from amnesia, forgetting the identity of Spider-Man and both his and his father's roles as the Green Goblin. Harry later married Liz Allen, an old high school friend of Peter's and had a son, Norman.
Once again, he remembered being the Green Goblin - and his irrational hatred of Spider-Man. Harry had convinced himself that Peter resented the Osborns' "stable family life" due to never having been wanted by his own parents or guardians, when in fact the complete opposite was true.
His sanity was shattered, he declared that their next confrontation would be their final one, and only one of them would be alive at the end. To ensure that he was the victor, Harry researched his father's chemical notes, hoping to recreate the original Goblin's superhuman strength. Harry made his own modifications to the formula, and upon ingesting it, it proved better than he had dreamed.
The formula had made him stronger than both Spider-Man and his father. Now a physical match for Spider-Man, Harry planned his final revenge.
Harry took to stalking Peter Parker on his Goblin Glider, claiming that there was no law against just soaring around town in a colorful costume, and taunting Peter that someday he would destroy him, but he relished keeping Peter in suspense in the meantime.
Harry Osborn appears in Spider-Man: The Animated Series, voiced by Gary Imhoff. This version was the son of industrialist Norman Osborn, a friend and briefly roommate to Peter Parker. Harry became attracted to Mary Jane Watson due to Peter neglecting her. Mary Jane subsequently left Peter for Harry. They became engaged, although she eventually called off their engagement realizing she was in love with Peter. When Norman was apparently killed in an explosion at Oscorp, the Green Goblin began kidnapping the Oscorp board members. Harry was initially suspect to be Green Goblin, but it later turned out that his father had survived the explosion and was the villain himself. When Green Goblin became trapped in limbo, he managed to contact Harry. The visions of his father had him take the serum and exact revenge on Spider-Man, with the villain promising to allow Harry to see his presumed deceased father. However, Spider-Man defeated the second Green Goblin and he was enrolled at Ravencroft to receive treatment. When Peter and Mary Jane were getting married, Harry discovered and his insanity broke out once again. He interrupted the wedding and threatened to destroy the church, trying to force Mary Jane to marry him instead of Peter. In the end, Liz Allan appeared to Harry, convincing him not to blow up the church nor marry Mary Jane. Told by Liz that he was loved, he walked away peacefully and the wedding resumed.
Harry Osborn appears in The Spectacular Spider-Man, voiced by James Arnold Taylor. This version is Peter Parker's best friend, high school classmate, and the son of Norman Osborn. This version shares many similarities to his comic counterpart considering the fact that he spends much of his life trying desperately to earn his father's approval, Harry takes the 'Globulin Green' serum to boost his physical abilities but apparently causes the development of a second personality which symbolizes his notion of "the man his father wanted him to be". Following several battles, Spider-Man comes to believe Harry is the series' iteration of Green Goblin but allows Norman to look after his son. After being on a European tour to help break his addiction to the serum, Harry returned from his trip. After Flash Thompson exposed Harry's addiction to league administrators and loses the trophy their team won as a result, Harry destroys the remaining 'Globulin Green' vials he kept hidden. Soon after, Harry attempts to have a relationship with Gwen Stacy though she expressed some anger when he overheard her talking about breaking up with him to Peter. During the series finale, Harry learned the truth of Norman being the Green Goblin all along as he witnesses his fight with Spider-Man up to his father's supposed death. At his father's "funeral", Harry has Gwen stay in their relationship out of guilt and Blams Spider-Man for his father's "murder", Harry, angry and mentally unbalanced, swears vengeance.
In Ultimate Spider-Man, he was voiced by Matt Lanter. He is portrayed as Peter Parker's best friend and classmate at Midtown High. In the pilot episode "Great Power", Harry is badly injured by Klaw when he tries to protect Peter and Mary Jane Watson from the Frightful Four. In the fourth episode, Harry, jealous of Peter's new friends (Spider-Man's teammates' alter egos), throws a huge party that is crashed by Venom. After Venom's defeat, a fragment of the symbiote is captured by Harry. In the episode "Back in Black", Harry bonds with the Venom symbiote (resembling Spider-Man's Black Suit) in an attempt to one-up Spider-Man, winning over everyone in the city, loving the new Spider-Man, even J. Jonah Jameson (although he still hated the original Spider-Man). But eventually, the symbiote's personality takes over and it attempts to destroy Spider-Man once again. Spider-Man electrocuted and seemingly disintegrated the symbiote, freeing Harry. However, the symbiote managed to survive and some of it was still on Harry. Harry returned as Venom in the episode "Venomous", in which Harry has no memory of being Venom, and Spider-Man tried to help him without exposing his identity to his teammates. Eventually, Spider-Man created an anti-venom that cured Harry and supposedly defeated Venom for good, but returned in "Rise of the Green Goblin".
In Spider-Man the Game, Harry takes on the role of the Green Goblin and investigates a plan to take over Oscorp and fights some of Spider-Man's enemies as well as a new unknown Green Goblin that has a deeper voice.
In the Spider-Man 3 video game, Harry assumes the identity of the New Goblin to take out Peter as a boss and later assists Peter in dealing with Sandman and Venom as a playable character. He is also a downloadable character on Xbox 360. In the limited edition of the game for the PlayStation 3, he is unlockable and is downloadable for the normal version as well.
He appeared in The Amazing Spider-Man 2 video game, and in this took on the role of the Green Goblin like in the film.
He was set up in Marvel's Spider-Man (2018) where he was on a trip to Europe, but later it was revealed that he was sick and kept in secret inside Norman's lab until he would find a cure.