Not many would've predicted the success of James Gunn's Guardians of the Galaxy. Whereas the likes of Iron Man and Captain America were already established names before taking the live-action leap, the unlikely collection of scavengers and criminals — led by Chris Pratt's Peter Quill — were much more obscure in the comic book world.

The group of outsiders who were thrust together more by pure chance than anything else, illustrated that expanding the MCU beyond one planet to the entire universe was a shrewd move. As well as critical acclaim for its funky, '80s inspired soundtrack, nebula-pallete saturation and well-timed humor, the movie generated an impressive $773.3 million. Not bad for a bunch misfits.

The debut outing of Star-Lord and friends was launched within a paradigm of little expectation, with a blank canvas the size of the Milky-Way to explore. But now the secret is out, Gunn has an interesting challenge: How do you build on the first film's success, while maintaining originality and tone in the sequel?

Crucially, the core of the group will all return. That includes Chris Pratt as Star-Lord, Zoe Salanda as Gamora, Dave Bautista as Drax the Destroyer, Vin Diesel as Groot and *deep breath* Bradley Cooper as Rocket Racoon. New additions need to be recruited wisely, picking only the best in the business to portray the baddest in the galaxy.

Who Will Join The Guardians Of The Galaxy?

Nebula has switched to the good [Credit: Marvel Studios]
Nebula has switched to the good [Credit: Marvel Studios]

With an entire galaxy to protect, Quill is in need of some reinforcements. In the first film Nebula (Karen Gillian), was a vicious and combative opponent to the Guardians, often clashing with her step-sister, Gamora. The pair were raised by the super-villain Thanos after he killed their parents.

Gamora had a change of heart of course, turning her back on Thanos due to his plan to destroy the planet of Xandar. Now, it looks like Nebula will follow course, although Zoe Salanda has confirmed that there will, unsurprisingly, be tension between the pair.

As well as Nebula's defection to the bright side, the team will have a new face in Mantis, played by Pom Klementieff. Raised by Ego (more on him later), she is a telepathic alien of immense power, once defeating Thor in the comic book world.

Even More Ravagers To Battle

Led by Yondu, the Ravagers had an interesting role in the first movie. Although they raised Quill, and Yondu in particular had a fatherly love toward him, Quill then betrayed them twice; firstly by taking the orb on his own accord, and secondly by not returning it as he had promised. At San Diego Comic-Con, Gunn confirmed they'll have an even more important role in Guardians of the Galaxy 2.

Yondu's lenience was a growing concern for the rest of the group, and it looks like we'll see some restructuring as Yondu defects to the Guardians. A new Ravager leader named Taserface (Chris Sullivan) will take his place. James Gunn's brother, Sean Gunn, will return as Kraglin, but he'll also be joined by Brahl (Stephen Blackehart), Scrote (Mike Escamilla), Oblo (Joe Fria), Narblik (Terence Rosemore), Gef the Ravager (Steve Agee), Wretch (Evan Jones) and Half-Nut (Jimmy Urine).

Ego The Living Planet

When it comes to characters, if you're looking to go bigger, you can't really go much further than an entire living, breathing planet. Ego The Living Planet will be played by Kurt Russell, and bizarrely will also be revealed as Star-Lord's father.

Putting questions and interesting visual images of how a planet would fornicate and reproduce to one side, Gunn confirmed that the relationship between Ego and Star-Lord would be one of the biggest themes running through the sequel.

Ego the Living Planet [Credit: Marvel Comics]
Ego the Living Planet [Credit: Marvel Comics]

In the comics, Ego was created by the enigmatic character Stranger, who gave a planet consciousness. He then began to create humanoid versions of himself, which may explain those puzzling questions from above. On Facebook, Gunn provided some context on the character. He said:

"I asked myself, if a planet was alive, how could that be? And how could it father a child? The answers to those questions took me to a far deeper place [than] I expected. I don’t want to give away too many answers at this time. But what Nova Prime said about Peter’s father at the end of [the first movie] is certainly true – he is something ancient and unknown."

And One We Don't Know Too Much About: Sylvester Stallone

The rumor mill was in full flow when the Hollywood icon was pictured leaving the hotel known to be frequented by cast of the movie. The exciting news is this has now been officially confirmed, meaning we'll see the action movie legend add some extra brawn in his cameo.

Sylvester Stallone has an unknown role [Credit: MGM]
Sylvester Stallone has an unknown role [Credit: MGM]

Early speculation suggested he could've played Quill's dad, although we now know this isn't the case. The teaser shown as Comic-Con gave a brief glimpse of Stallone interacting with Yondu, which could suggest he's a potential member of the Ravagers, or perhaps joining with Irani (Glenn Close) by trying to maintain peace with the Nova Corps.

What do you think of the additional cast members for Guardians of the Galaxy 2?