The members of this cult of Loki regularly share pictures and memes via social media and dress up in green-and-gold costumes and wield scepters for comics conventions. Most important, they've built a community around a guy who probably should get booed but is instead cheered for his mischievous nature.

The Dark World shows that Loki isn't just a one-note villain, says Hiddleston. The character's previous on-screen appearances showed malevolence along with nuance. Loki learned he was adopted in the first Thor, for example, and The Avengers highlighted the fractious relationship between him and his half-brother Thor (Hemsworth).

That continues in the sequel, which has the siblings teaming up, albeit tenuously, to seek vengeance and go after the leader of an ancient race of dark elves, Malekith (Christopher Eccleston). The villain aims to destroy the Nine Realms, including the siblings' home of Asgard, as well as Earth.

"The Dark World is where we really get into the nitty-gritty at home" with Thor and Loki, Hiddleston says. "It's the meat and potatoes, the muscularity of their relationship and particular chemistry that can yield enormous drama, battles of wits and wills and also, thrillingly, some humor."

That balance of the serious and a sense of humor is key to why Loki plays so well in the movies, says Kevin Feige, Thor producer and Marvel Studios president.

"It's a rare gift to be able to get away with the evil things he does over the course of these films and still have people like him and like the bad boy," he says. "That's mainly because Tom is so charismatic and also because you see underneath that grin the real pain. He says in this movie, 'Trust my rage,' and you completely buy it."

Based on Norse mythology, the comic-book version of Loki was introduced by Stan Lee and the late Jack Kirby as Thor's arch nemesis in 1962. A year later, Marvel Comics cast him as the primary villain in the historic The Avengers No. 1.

In recent years, Loki has been revamped as a teenage antihero in the titles Journey to Mystery and Young Avengers, and he's being reinvented next year, espionage-style, as the gender-shifting star of writer Al Ewing's Loki: Agent of Asgard comic.

"He's a trickster, and by his nature as a creature of myth he invites the writer to play tricks as well," Ewing says.

Ewing notes that Loki's popularity isn't actually new — he essentially is a religious figure whose stories and sagas have been around for centuries.

As for the movie character's move into the pop-culture zeitgeist, "people do like a sexy bad guy with lots of screen presence, and he's definitely that," Ewing says. "But what makes it special is the vulnerability — there's anger there, not all of it unjustified. That makes him easier to empathize with than if he was just a cackling mustache-twirler."

Loki technically may be a supporting player in Marvel movies, yet for some he's the main event. After Hiddleston "crashed" a Thor Comic-Con panel in character in July in San Diego — to the delight of 6,500 fans — Denise Heard-Bashur thought a Loki movie sounded like a great idea, so she started a petition. Her group Free Loki has rounded up more than 30,000 signatures, but it's also taken inspiration from Hiddleston's work with UNICEF to raise money for Operation Smile.

"He goes out of his way to appreciate his fans, treating them as a blessing rather than a curse," Heard-Bashur says of the actor. "Not to mention, the man is dangerously beautiful in an almost ethereal way."

Aside from making Loki aesthetically pleasing, Hiddleston crafts a figure who rides a line between redemption and sin and is relatable to many.

"It's hard to fully identify with heroes because most of us don't believe we're capable of so much honor and bravery, whether we are or not," Heard-Bashur says. "What we can believe is that we've been wronged somehow, that we're alienated and scarred.

"For some reason, this is never hard for us to accept as human beings. In that, we can look at Loki and say, 'Exactly!' "

Taylor echoes the feeling that it was a bit of flawless casting.

"James Gandolfini almost didn't play Tony Soprano and Jon Hamm almost didn't play Don Draper. But once those guys are there, it feels like you can't see past them to any other options," the director says. "I feel the same with Tom playing Loki."