The movie contains elements from the classic comic series and the more recent series: The team roster is taken from the current series, but Peter Quill is raised by Yondu, who was a member of the original team from the 60's.
Lee Pace has said that Ronan works under Thanos, much like the Ultimate Marvel version of the character.
Though he eventually learns the error of his ways, Star-Lord starts off as a self-serving outlaw and a bit of an asshole. This is in contrast to his comic counterpart, who was a seasoned cosmic superhero long before joining the Guardians. It's really more of an Adaptational Anti-Heroism situation if anything.
While Ronan the Accuser has never been the nicest guy in the main Marvel comics 'verse, in his role as Supreme Accuser of the Kree Empire he was basically a Knight Templar. Here he's a renegade who's collecting the Infinity Gems for Thanos. His actor compares him to Osama bin Laden. He also looks more Obviously Evil.
The Alcatraz: The Guardians spend some time imprisoned in The Kyln space prison and have to escape.
Rocket: They call the Kyln the stomach of the prison system. Now matter how good you are going in, you come out pretty frickin' bad.
Big Bad Duumvirate: Nebula and Ronan serve as the film's two main antagonists, both seeking to obtain the MacGuffin Peter stole for their mutual employer.
Big Good: Nova Prime Rael, the leader of the Nova Corps.
The Big Guy: You've got two in the team. Drax is already a pretty big man himself, but Groot is bigger and can grow in size like his comic counterpart.
Bigger Bad: Thanos. Most of the film's villains act as his servants, and he will apparently appear in person.
Bilingual Dialogue: Rocket and Groot understand each other fine...even though Groot can only say "I am Groot."
Bizarre Alien Biology: Rocket looks like a regular earth raccoon, but is tough enough to hoist a gun bigger than he is and shoot it without breaking his arms. Also he can talk. And he has no idea what a raccoon is.
Groot is... a tree. A sentient tree. Who talks only in Pokémon Speak and can spontaneously grow his limbs, extend spines or vines from his body, or release glowing spores. In the comics, he can grow to nearly 30 feet tall and is nigh-impossible to kill, regrowing from a sprig even if he's destroyed. He is also of royal lineage, and is a scientific genius.
Black and Gray Morality: There's no doubt the baddies are on the side of evil since Thanos is their big boss. However, the "good guys" have done morally questionable things.
Vin Diesel got cast as the quietbig guy Groot in part because he was the voice of The Iron Giant. Hell, he's even working with the same sound technician for his voice-over sessions.
Cain and Abel: According to the Prelude comics, Gamora is the Abel, and Nebula is the Cain when they were still batting for the same team.
Cloudcuckoolander: Groot, being a sentient tree, is expected to be a little less-than-rational, but Drax is shaping up to be the antithesis of the brooding, revenge-driven psychopath, and instead is a ditzy revenge-driven psychopath.
Cyborg: Rocket Raccoon is an illegal experiment in cybernetics, and his cyborg parts are visible when he's not wearing clothes. Nebula also has a cybernetic eye and arm. Korath also has visible machinery sticking out of his head.
Peter: I look around, and you know what I see? Losers! [beat] I mean, like, folks who have lost stuff. Our homes, our families. And we're facing a threat that could destroy us all. ... But life is giving us a chance. Drax: To do what? Peter: Something good... something bad... bit of both.
Dude, Where's My Respect?: Nobody knows who Star-Lord is, and the team is regarded mostly as "a bunch of a-holes", even though they are trying to keep a reality-destroying MacGuffin from one of the most powerful beings in the universe.
Funny Background Event: As Rocket argues with Quill and Gamora about a hard to get component for his escape plan, Groot just walks over, grows his arms and legs to reach it, and grabs it. Meanwhile, Drax has wandered over and simply watches Groot the whole time.
Getting Crap Past the Radar: In the trailers, when Star-Lord flips off the Nova Corps, the local computer system catches on and throws up a holographic blur filter, complete with a tooltip explaining "Obscene Gesture Imminent." It's uncensored in the actual film.
Glory Hound: Peter Quill fashions himself as a legendary outlaw. Unfortunately, no one's ever heard of him.
Honey Trap: Rocket suggests Gamora does this to get some components for his escape plan.
Gamora: How are we supposed to do that? Rocket: Well supposedly these bald bodies find you attractive, so maybe you can work out some sorta trade. Gamora: You must be joking. Rocket:No. I really heard they find you attractive.
Human Aliens: The Xandarians all look human, despite being from an alien world lightyears away from Earth.
Indy Ploy: The revelation and argument over Peter's 'plan' is an entire scene on its own.
Peter: I have a plan. Rocket:You've got a plan?! Peter: I have part of a plan!
Jerk with a Heart of Gold: The entire team according to James Gunn - save Groot, who's gentle-natured to begin with. They may all be criminals, but they're still willing to stick their necks out if it means protecting billions of innocents.
The Napoleon: Rocket Raccoon is 4 feet tall, carries a gun bigger than he is, and has no qualms blasting your face off with it.
Non-Indicative Name: They're a bunch of thugs and criminals, little more than a gang, and not some uber-powerful cosmic superteam. Calling themselves the Guardians of the Galaxy is probably an ironic, Small Name, Big Ego kind of thing.
Non-Uniform Uniform: The members of the team eventually gain red, military-like uniforms, but each one has some noticeable variations. Drax doesn't even wear a shirt with his.
Drax was originally a Caucasian man named Arthur Douglas in the comics. Here, he's played by the half-Filipino/half-Greek Batista. To say nothing of the fact that Drax is an alien in the movie but human in the comics.
Korath the Pursuer is black rather than blue. This is notable because in the comics, it's an explicit plot point that the Kree only come in two types: a blue-skinned majority and a white-skinned minority, the latter of whom experience Fantastic Racism from the former.
Red Oni, Blue Oni: One's a 4-foot tall cybernetic raccoon who likes his big guns. The other is a (normally) 7-feet tall Gentle Giant of a tree who doesn't mind busting heads. Together, they will kick your ass from one end of Knowhere to the other.
Sequel Hook: James Gunn has said what happens in the film is important to the plot of the third Avengers movie.
Serkis Folk: Along with voicing the character, Vin Diesel also portrays Groot via motion capture, even wearing stilts to match Groot's height.
Shout-Out: The first scene in the initial trailers, showing Peter Quill about to steal something, leans hard on the opening sequence in Raiders of the Lost Ark and later, he even lampshades this later in prison along with The Maltese Falcon in order to explain the mystique surrounding the Orb.
This is also the first Marvel Studios film not to feature Avengers members.
In fact, this is the explicitly stated reason as to why this movie is happening. After nine or so straight movies revolving around the members of the Avengers, building up to the upcoming finale to Phase Two, The Avengers: Age of Ultron, Guardians of the Galaxy is a Breather Episode gathering of C-list and D-list Marvel characters that nobody would ever expect to be featured in a film.
The second trailer gives us "Spirit In The Sky" by Norman Greenbaum.
In a Facebook chat, it was hinted (and then outright mentioned by Chris Pratt) that "O-o-h Child" by the Five Stairsteps will be included as well.
The second trailer also reveals that these songs are contained on a cassete tape of Peter's, labelled "Awesome Mix #1." Groot seems unimpressed.
The official soundtrack consists of various seventies and eighties hits, including "I Want You Back" by the Jackson 5, "Escape (The Pina Colada Song)" by Rupert Holmes, and "Moonage Daydream" by David Bowie.
In the film, Hooked on a Feeling plays while the Guardians' are inducted into a high-security prison.
Source Music: The 70s and 80s tunes that play in the movie are all from an eight track tape that Peter owns and listens to regularly in the film itself.
Spanner in the Works: Rocket had this elaborate plan laid out to break out of prison, and Groot, well-meaning tree that he is, proceeds to immediately grab the item that they were supposed to grab last, which triggers the prison alarms. The rest of the team have to quickly improvise the rest of the escape.
Starfish Language: It sounds like all Groot can say is "I am Groot", but he's actually very intelligent and well-spoken, and that's just how his subtle and complex language sounds to people no matter what he says. Helpfully, Rocket can understand him.
Stealth Pun: The third trailer includes the Tag Line "All Heroes Start Somewhere." After the word "Somewhere" appears on screen, the next thing you see is a space station. The name of that space station, not mentioned in the trailer but known to followers of the comics? Knowhere.
Straight Man: Gamora is shown trying to wrangle the boys to formulate a cohesive plan and fails hilariously.
Rhomann all but vocalizes this when he realizes that the fate of the galaxy rests on the so-called Guardians.
Rhomann: This might not be the best idea.
Title Drop: Star-Lord, Rocket Raccoon, and Rhomann Dey all get to do this.
Token Good Teammate: Groot is the only Guardian that doesn't start the film as a criminal or Jerkass; the only reason he's with them is because of Rocket. Word of God notes that he's essentially "innocent" compared to the others.
Unexpected Character: The movie is pretty much a gathering of C-list and D-list Marvel characters that nobody would have expected to be featured in a film. And by C-list and D-list characters, we mean a bunch of dudes who could give The Avengers a run for their money in the ass-kicking department.
Wretched Hive: The Knowhere space station, a severed Celestial head located at an unspecified place just outside of spacetime. It's a port of call and observatory for intergalactic travellers, and so attracts all sorts of unsavory characters.
You Are Number Six: Rhomann Dey refers to Rocket by the serial number used by the scientists who created him.