- Anti-Villain: They may be delinquents but they are loyal to each other, and trying to cope in an impoverished reality.
- Delinquent: When your introduction is basically "a gang of teen muggers decide to pick on a nurse on Bonfire Night", you've hit this trope. Deconstructed, though: given their various backgrounds, they don't have many other readily available options. The more the film goes on, the more humanisation for the audience they get.
- Don't Tell Mama: A common theme with those who have family who care. "Playing video games at a mate's..."
- Five-Man Band
- The Hero - Moses - The clear leader of the group.
- The Lancer- Pest - He gives Moses a lot of support.
- The Big Guy- Dennis - The most hotheaded of the group.
- The Smart Guy- Jerome - Probably the most level-headed one - and he has glasses.
- The Chick - Biggz... well he does spend half the movie hiding in a dumpster.
- Hidden Depths: All of them, even the tag-alongs Probz & Mayhem, have surprising levels of expertise and characterization hidden within some of the daft stuff they say and pull.
- The Yardies: Or, at least, the kids of Yardies and apt to take up the trade. These guys are third or fourth generation, but still stuck in Estate life.
A quiet teenage gang leader and orphan looking for respect around the Block.
- Anti Hero: Moses is a low-level criminal and mugger on the verge of becoming a drug dealer but he's also a brave, loyal person in a difficult place in life.
- Badass Biker: Moses is the only one who doesn't crash his bike at any point.
- Held Gaze: Dude rocks this as a whole communication style.
- Hidden Depths: Much of the film revolves around the fact that there's more to Moses and his friends than meets the eye. Moses might be a low-ranking mugger, but he has a sense of honor and a difficult home life.
- Implied Love Interest: Moses and Tia seem to hold some romantic interest in each other.
- Red Oni, Blue Oni: He's the blue to Dennis's red.
- Standardized Leader: He often comes off as this.
- Younger Than They Look: Given the way he looks and acts, you'd swear he must be between eighteen and twenty. It turns out he's only fifteen.
Moses' smart aleck second-in-command of the gang.
- Batter Up!: Uses an aluminum bat as his backup weapon.
- Buffy Speak: You can thank him for coining the term Big alien gorilla-wolf motherfuckers to describe the aliens.
- Deadpan Snarker: The most sarcastic of the group.
- Fatal Fireworks: Uses fireworks as his main weapon.
A hotheaded pizza delivery boy and member of the gang.
- The Big Guy: The most hotheaded of the group and the first to brandish the katana.
- Big Guy Fatality Syndrome: Hes the first of the gang to die.
- Car Fu: Uses a police van to kill one of the aliens.
- Hot-Blooded: He's easily the most aggressive and quick to anger out of the gang.
- Red Oni, Blue Oni: He's the red to Moses's blue.
- Token Evil Teammate: He's the most unpleasant gang member and is perfectly willing to leave Sam to die because he views her as an annoyance.
A schoolboy and member of the gang.
- Machete Mayhem: Picks up a machete as his weapon.
- Nerd Glasses: He wears a thick pair of glasses.
- Only Sane Man: He's often the voice of reason and the most level-headed in the gang.
- Token Good Teammate: Not that the rest of the gang are evil, but Jerome is the most blatantly likable and even-tempered member. He sympathizes with Sam and certainly doesn't enjoy the mugging, even less so than the other members.
The youngest member of the gang.
Other Block Residents
Samantha "Sam" Adams
A nurse and new resident of the Block.
- Deadpan Snarker: She has a subtle wit exasperated by the...'challenging' circumstances.
- Held Gaze: Frequently with Moses.
- The Medic: She's a recently graduated nurse.
- The Not-Love Interest: A key dynamic of the film is her relationship with Moses, but it's never romantic. It's a gradual development of understanding, respect and friendship after an initial antagonistic encounter.
The local weed dealer who lives in the penthouse of the Block and knows everyone.
- The Stoner: Well, he does deal weed. It's a professional side effect.
Ron's feared boss and the local psychotic gangster of the Block.
- Ax-Crazy: Hi-Hatz is as bloodthirsty as the aliens; he swings from mood to mood, kills when he feels like it and pulls out his gun at the slightest provocation. He actually gets progressively worse as the night goes on.
- Big Bad Ensemble: He's the main human antagonist.
- Cruel and Unusual Death: He gets pinned down by a horde of aliens zombie movie style and Eaten Alive.
- Drives Like Crazy: To the point where it's a wonder that he's alive in the first place.
- Establishing Character Moment: Introduced while singing along to a rap song about shooting a snitch.
- Faux Affably Evil: Extremely faux. Even Mayhem and Probz don't seem fooled by his friendly act, and just give him information to get him out of their hair.
- Only Known by Their Nickname: His real name isn't revealed; the Block knows him solely as Hi-Hatz.
- X Treme Kool Letterz: It's right there in the name.
A resident of the Block.
- Action Girl: The girl is a serious badass; when aliens attack, she barely hesitates to attack right back.
- All Girls Want Bad Boys: Subverted; she's implied to have a crush on Moses, but is highly critical of his criminal lifestyle.
- Improvised Weapon: Picks up a lamp and breaks it to make a makeshift taser.
- Screw This, I'm Outta Here!: She, Dimples, and their friends flee the block when Dennis is killed.
- What the Hell, Hero?: She gives a few of these to Moses.
A resident of the Block.
- Improvised Weapon: Uses an ice skate to kill an alien.
Reginald & Gavin A.K.A. Probs & Mayhem
A student stoner and one of Ron's customers.
- Author Avatar: Joe Cornish has admitted that Brewis is his stand-in; a well-meaning but dorky and inept young stoner.
- Chekhov's Skill: Brewis' stoned intake of nature documentaries turns out to be quite useful with regards to theorizing on the nature of the aliens.
- Erudite Stoner: For the entirety of his screen-time he's at least semi-high, but no less coherent.
- Pretty Fly for a White Guy: He's introduced hilariously lip-synching to KRS-One. He later tries to bond with the Gang, but he's clearly a middle-class dork and they aren't impressed.
The main antagonists of the film, the unnamed Aliens are ferocious beasts that rain from the sky to wreak havoc on the Block and its inhabitants.
- Aliens in Cardiff: Gorilla-wolf motherfuckers in a South London slum.
- Bioluminescence Is Cool: They have glowing neon teeth.
- Bizarre Sexual Dimorphism: The first, small alien killed at the beginning is in fact a female, while the males are hulking, black ape-like beasts.
- Dark Is Evil: The aliens are black, so black that they seem to absorb all light and none of their external features can be easily seen, save for the neon-blue teeth.
- Dead Guy on Display: The first small alien, after being killed by the gang, is paraded around like a trophy by the boys, which backfires on them horribly later on.
- Eyeless Face: Both types of alien have no eyes, relying on echolocation and smell.
- Lightning Bruiser: Are very fleet of foot, and can even outrun the boys on motorcycles!
- Made of Iron: The film does a good job showing the aliens as tough but not invincible. Tia and Dimples are able to take one down but only after electrocuting it, covering it with a blanket to disorient it, then repeatedly pummeling it with lamp stand and an ice skate blade for several minutes. On the other hand, another alien takes six bullets from Hi-Hatz and still manages to slaughter both of his companions.
- More Teeth than the Osmond Family: And they glow in the dark!
- Pint-Sized Powerhouse: Though it is killed by Moses and the gang, the first small alien manages to put up quite a fight and wounds Moses in the process.
- Super-Persistent Predator: They chase down the boys through the block and manage to find them despite there being hundreds of rooms in the building! Turns out they were following the scent of the female alien that Moses killed.