Fifteen years after the premiere of "Justice League," DC Comics' greatest heroes return to animated television Friday, Dec. 16, in the United States with "Justice League Action," and they've brought along some friends. A lot of friends.

Produced by Warner Bros. Animation, the new Cartoon Network series probably has more in common with "Batman: The Brave and the Bold" than with "Justice League" or "Justice League Unlimited," as it teams DC icons -- first and foremost, Superman, Batman and Wonder Woman -- with a roster of lesser-known heroes. Oh, and there are plenty of villains, too, both big and small, from classics like The Joker to Chronos, to newer nemeses like Dex-Starr.

RELATED: New "Justice League Action" Trailer Assembles DC's Greatest Heroes

"Justice League Action" also eschews the traditional 22-minute animated format in favor of 11-minute episodes, which means the emphasis will be on, well, action. It's right there in the title.

To get you ready for the series premiere, we've broken down everything we know (so far) about "Justice League Action."

It Was Originally Planned as a Batman Series

justice-league-action-header

Although the short-lived "Beware the Batman" had ended only in 2014, the project that would become "Justice League Action" was supposed to be Cartoon Network's latest Batman cartoon.

"Originally, we were supposed to be doing another Batman series," producer Butch Lukic, whose credits include "Batman: The Animated Series" and "Batman Beyond," revealed in July at Comic-Con International. "But me and Alan [Burnett] got together with the whole team and then eventually, a week later, it was suggested we do a Justice League show instead. There was a gap between a new series [and the last one], plus the new movie is coming out, so we got the go-ahead to do a Justice League series."

Season One Features More Than 150 DC Characters

justice-league-action-stargirl

Well, 152 to be exact. Of those, Lukic said about 60 are superheroes, 40 are villains, and the remainder supporting players. Most of the episodes will feature at least one of DC's Trinity -- Batman, Superman and Wonder Woman -- partnered with a veritable who's who of the DC Universe (seriously, you may need to dust off a copy of "Who's Who in the DC Universe"). Along with the likes of Hawkman, Stargirl, Blue Beetle and Plastic Man, between the Comic-Con highlight reel and leaked concept art we've seen such characters as Mongul, Big Barda, Doctor Light, Shazam, Vixen, Mr. Terrific and Killer Croc. But that barely scratches the surface.

DC Entertainment approached the series with a clear idea of which character should appear. "They gave us a list at first,” Lukic said. “That was based originally on the [New] 52 comics. The list of characters in there were what they wanted, and it was pretty much the ones everyone wants, plus some odd ones. We definitely got most of those in, plus a few that we thought of that would fit.”

Expect the Unexpected

justice-league-action-demon

Unexpected team-ups, that is. As you might expect from the eclectic cast of characters, some of the pairings are unusual, to say the least. For instance, in the highlight reel we see Batman with Etrigan the Demon and Wonder Woman take on Lobo, while in one of the clips Superman seemingly "rescues" The Joker from Mongul.

According to Lukic, both John Constantine and The Demon appear in "quite a few early episodes," and the Demons Three even show up. "I think you're going to find that many DC stones have been turned," producer Jim Krieg promised. "We've pulled out those worms and put them in the show."

justice-league-action-wonder-woman2

The First Episode Features Shazam and The Wizard

See? You probably weren't expecting that.

In "Shazam Slam," Black Adam battles Batman on the Rock of Eternity, home of the Wizard Shazam -- apparently referred to on "Justice League Action" simply as The Wizard -- and unleashes a djinn horde determined to return Earth to its pre-human state. The Caped Crusader is transformed into an enormous flying Batmonster that lays waste to the Hall of Justice, and only Superman is powerful enough to stop him. The rest of the Justice League, aided by Shazam (voiced by Sean Astin) and The Wizard (voiced by Carl Reiner), must hunt down and defeat each of the djinn to save the planet from destruction.

Kevin Conroy Is Batman (Again)

justice-league-action-batman2

Acclaimed voice actor Kevin Conroy, who's portrayed the Dark Knight in animation and video games for the better part of 25 years -- from "Batman: The Animated Series" to "Injustice: Gods Among Us" to "Batman: The Killing Joke" -- reprises the role on "Justice League Action," joined by frequent collaborator Mark Hamill once again as The Joker. Diedrich Bader, who voiced the Caped Crusader on "Batman: The Brave and the Bold," steps into the role of Booster Gold in the new series, conceding that Conroy is Batman.

"All I do is a poor imitation of Kevin, so to be in a session with him was really, really great," Bader said at Comic-Con. "I totally geeked out on him!"

"I'd love to say that I'm doing all these different versions of the character," Conroy said, reflecting on his quarter-century as the Dark Knight, "but the trick I've found is consistency. I have to be consistent. Batman's audience is fanatically devoted. They know more about him than I do. They know everything about Batman, and they have a very personal relationship with the character because they grew up with the character. If I do anything that even sounds slightly inauthentic, they'll nail me on it. They'll hear it. You can hear inconsistency, and you can hear inauthenticity faster than you can see it."

You'll Recognize A Lot of the Voices

justice-league-action-brainiac

In addition to Conroy, Hamill and Bader, there are plenty of other voices in "Justice League Action" that will undoubtedly stand out to viewers. Khary Payton reprises his "Teen Titans" role as Cyborg, joined by Brent Spiner as The Riddler, James Woods as Lex Luthor, John DiMaggio as Lobo, John de Lancie as Brainiac, Hannibal Buress as Mr. Terrific, Michael Dorn as Atrocitus, Ken Jeong as Toyman and the aforementioned Sean Astin and Carl Reiner as Shazam and The Wizard, respectively. And then there's Cloris Leachman, known for "The Mary Tyler Moore Show," "Wonder Woman," "Young Frankenstein" and "Raising Hope."

"It’s an amazing cast!" Conroy said. "I think it’s because everyone wants to do animation now. Everyone wants to do it. They can get any actors they want. Cloris Leachman! I couldn’t believe it! The day I worked with her, I told her, ‘I’ve never forgotten you from “The Last Picture Show.” It was one of the most heartbreaking performances I’ve ever seen.’ Her eyes lit up: ‘No one ever mentions that anymore! I can’t believe you saw it!’ Saw it?!? It’s a landmark film! So to have her on the cast is great.”

It Contains Humor, But It's No "Teen Titans Go!"

justice-league-action-firestorm

For the comic book faithful, that's probably a good thing, as the surreal and often slapstick "Teen Titans Go!" has proved as divisive as it is popular.

"It's definitely a Justice League action show," Conroy acknowledged. "It's got all the action and the drama of a 'Justice League' episode. But those characters -- all those characters, Batman, Superman, Wonder Woman -- there's always that sort of temptation to tweak them a little bit."

“We wanted to do a show for kids, to appeal to boys in particular,” said producer Alan Burnett, whose extensive credits include "Batman: The Animated Series," "Superman" and "Batman: The Killing Joke." “At first, the show was a lot more action-y than it turned out to be, because as we got more into it, we found that the action played better with some comedy, some character quirks. So it is, in a way, an action show with comedy. But the action’s always serious, the fighting’s always serious. We ended up producing a show that I think is going to get a lot of kid attention. It’s a show that parents can watch along with their kids.”

There's No Robin ... Yet

There may be 60 DC heroes in the first season of "Justice League Action," but none of them is Robin -- Dick Grayson, Jason Todd, Tim Drake, Damian Wayne or otherwise. (Although he is referenced in the Toyman episode.) However, Lukic said, that will likely change with Season Two.

That said, DC's younger heroes are represented, with appearances by Jaime Reyes/Blue Beetle, Stargirl, Supergirl, Cyborg and Ronnie Raymond/Firestorm, who, judging by the highlight reel, is enthusiastic but inexperienced and a little star-struck, suggesting he may be teen- or college-age.

Two Words: Space. Cabbie.

justice-league-action-space-cabbie2

Ingenious in its simplicity, Space Cabbie arguably represents the best of silly 1950s sci-fi comics. He drives a cab ... in outer space! Introduced in 1954 by Otto Binder and Howard Sherman, he chauffeured 22nd-century passengers to Pluto, Venus and beyond, frequently becoming embroiled in their affairs, or else getting into trouble of his own.

A staple of DC's "Mystery in Space" for four years, Space Cabbie has popped up for the occasional cameo in comics like "The Books of Magic," "Starman," "Justice League Unlimited" and "Lobo," where he's enlisted by the Main Man to chase down space bikers. Now he reemerges on "Justice League Action," where he's voiced by Patton Oswalt and may reunite with the Scourge o' the Cosmos. Let's hope it goes better for Space Cabbie than their first meeting.

"DC wanted him involved in the series, and he turned out to be a good choice," Lukic said. "We definitely can go a lot of places with Space Cabbie."

"Justice League Action" premieres Friday, Dec. 16, at 6 p.m. ET/PT on Cartoon Network before moving to its regular Saturday time slot on Dec. 24. The series debuted this morning in the United Kingdom.