A character from the
Marvel Comics universe. There have been no less than 5
Green Goblins.
The first one was Norman Osborn, and he made his first appearance in Amazing Spider-Man #14. He tried out an experimental serum on himself that gave him super-strength, made him smarter, and endowed him with a healing factor. It also slowly drove him insane. He was responsible for the death of Gwen Stacy, and was impaled on his own glider during that same battle. But that healing factor I mentioned saved his life (and left him with a wicked scar), and he went into hiding over in Europe for a period of time. He has since revealed himself to be the mastermind behind the clone saga, and has done his best to make Spider-Man's life hell. This includes hiring a woman to cause Mary Jane to go into premature labor, and then steal the baby. He also made Spidey think that his Aunt May was dead, while he kept her captive for a year or so. He went completely nutty in a magical ritual which gave him the "gift" of madness, but drugs keep that in check. Lately, he decided to make Spider-Man his heir apparent, but gave up on that when Spidey proved to be to much trouble. He was succesful in breaking Spider-Man's spirit, causing Spidey to doubt himself and his nobility.
Norman's son, Harry, was the next to take up the Goblin mantle. He first appeared in Amazing Spider-Man #31, although he didn't become the Green Goblin until Amazing Spider-Man #136. He was already half-insane due to drug problems when he found out that his father was the Green Goblin. He took a version of the Goblin serum that made him stronger than the original would, although it lacked the healing factor. He died in Spectacular Spider-Man #200, apparently due to side effects from the serum. He's still dead, for now.
The third Goblin was Dr. Bart Hamilton, who first appeared in Amazing Spider-Man #167. He was Harry's psychoanalyst, and got a few ideas after listening to Harry talk about being the Goblin. He fought Harry while both were Goblins, and blew himself up in Amazing Spider-Man #180.
The fourth Goblin was Phil Urich, nephew of Ben Urich, the Daily Bugle reporter. He stumbled upon one of Norman Osborn's abandoned labs, where he was doused with a special Goblin serum. This serum gave him all the Goblin's abilities, but only when used in conjunction with a special Goblin mask. He used his powers to fight crime, but after a short run, his series was cancelled. Phil had the Goblin costume taken from him by a company owned by Norman Osborn. Norman was just eliminating the competition.
The fifth Goblin was simply an artificially created being to keep people from suspecting that Norman was the Green Goblin by confronting him so the two would be seen in the same place at the same time. This Goblin just sort of melted.
So, Norman has been the only one to perservere throughout the years. He remains a constant thorn in Spider-Man's side.