Brian Truitt

USA TODAY

Even after 25 years, comic-book artist Rob Liefeld still can’t home in on a single reason exactly why Deadpool, Marvel's resident "Merc with a Mouth" and Hollywood’s spankin’-new movie star, is so popular among fans.

Instead, there are quite a few. He has a neato red-and-black outfit. He breaks the fourth wall regularly. He does serious damage with guns and katana swords. He lives for chimichangas and Bea Arthur. And he’s a total wisenheimer.

“Characters with attitude, we migrate to them all the time,” Liefeld says.

Ryan Reynolds as Deadpool admits his own 'Wolverine' failure

The antihero doesn’t have the mainstream recognition of Captain America or Batman, but that could change with Deadpool (in theaters Friday), directed by Tim Miller.

He's a Marvel character, but isn't part of Disney's Marvel Cinematic Universe; instead, he's in Fox's X-Men movie world.

The R-rated action comedy stars Ryan Reynolds as Wade Wilson, who turns to some shady figures to cure his cancer and ends up a wisecracking disfigured warrior with an obscenely good healing factor. So Deadpool isn't exactly a patriotic super-soldier like Cap or a muscular thunder god like Thor.

“He’s such a relatable, self-loathing nutcase, and a voice that was so unique in this superhero space,” says Paul Wernick, who co-wrote Deadpool with Rhett Reese.

After playing a unmasked, silent version of the character in 2009's X-Men Origins: Wolverine, Reynolds, a longtime Deadpool fan, started working with Wernick and Reese on a script that was truer to the motor-mouthed comics persona.

It was a rough road, Reese says. “This movie died so many times. It is much like the character: It rose up off the floor after multiple grievous mortal wounds.”

As much it has been a passion project for the moviemakers, Deadpool means more to Liefeld. He introduced the character in 1991 alongside fellow New Mutants writer Fabian Nicieza, and the antihero, influenced by both Boba Fett and Spider-Man, was an immediate success.

Ryan Reynolds surprised fans at a 'Deadpool' screening

He launched the mutant superteam X-Force that same year with a first issue featuring Deadpool that sold more than 4 million copies, the second-best-selling comic ever. In his early 20s at the time, he was trying to both make his mark in the industry while also caring for his family — his father had undergone six surgeries for cancerous brain tumors since Liefeld was in sixth grade.

“That period of my life, I had to succeed,” says Liefeld, whose Deadpool: Bad Blood graphic novel is out this year.

Deadpool is one of most recent Marvel characters to connect with comic fans in a major way, says Jermaine Exum, general manager of Acme Comics in Greensboro, N.C. However, he isn’t a kid-friendly character, Exum warns. “The Deadpool movie is the Red Ryder BB gun from A Christmas Story.”

Yet Wernick thinks Deadpool can fill a hole in the superhero marketplace with sex, four-letter words and extreme violence. “Marvel can’t make these kind of movies. We can and we should.”

Liefeld is all for it. “We’ve had a steady diet of that PG-13 entertainment,” he says. “It’s the best vanilla you can buy. It’s delicious but it’s getting kind of samey. This is mint chip, a new flavor. People are going to be like, ‘I want more of this!’ ”