This film contains all sorts of extremely graphic and gruesome bodily transformations, with people being infected by parasites and transforming into absolutely inhuman monstrosities. James Gunn went crazy with the body horror, and it overall goes on par with "The Thing (1982)".
All of the violence is very tongue-in-cheek and not to be taken very seriously, but it can get pretty intense nonetheless.
A man (hereinafter referred to as the "slugman") changes as an alien invades more of his body: it starts with a rash, then moves to tentacles pushing out through his abdomen (we hear crunching, then see something moving under his shirt, then the tentacles poke though), then other tentacles protrude from his head, and eventually he becomes a blob of throbbing tissue with deadly tentacles and a deformed human face.
A man and a woman prepare to have sex by removing their shirts, but when the man removes his, he reveals two wriggling tentacles; the man forces himself on top of the woman, she screams, he holds her mouth, the tentacles force their way into the woman's abdomen, and the woman thrashes with what looks like sexual movements.
A man is struck by the slugman's large tentacle. At first he seems he's okay, but then a small cut appears down his face and his whole body then splits in half, with all of his organs spilling out. Very gory and disturbing.
The slugman slithers across a field, slashes the throat of a cow (we hear the slash and squish and see the cow fall with a bloody neck wound), and the slugman drags the carcass away.
Large slugs force their way into the mouths of many people: the people lurch and thrash, and their mouths bleed; they then fall motionless only to become reanimated later.
A large slug swims toward a young woman who is taking a bath, she screams, gets out of the tub, and the slug sticks to her back and shoots into her mouth; she then bites it and pulls on it while blood dribbles from her mouth, and she pulls it out, throws it against a wall, and burns it with a curling iron.
A woman walks into a dark basement, the body of a dead dog falls in front of her, she turns on the light and sees bloody body parts and animal carcasses covering the floor and hanging from the ceiling, dripping blood.
We see many dead animals in a field, one dog is cut open from throat to abdomen (it's very bloody), and another dog is beheaded -- the head is found elsewhere.
A husband knocks his wife to the floor, opens his shirt, tentacles try to get inside her abdomen, she hits him in the head with a table, his arm becomes rubber-like and wraps around her neck, police with guns enter the room and the man runs away.
What looks like a blood-soaked deer eats from the dead carcass of something else (it isn't clear what), it jumps on and attacks a man trying to bite him, and a young woman knocks it in the head with a fire extinguisher.
A large slugman is shot, he explodes and sprays matter and blood everywhere.
A man in the distance is being killed by several re-animated people, as he screams and thrashes.
We see several re-animated people moving toward a large slugman and we are told they are "joining" and they seem to be absorbed into the slugman's mass.
A man finds himself in a dark place, he hears slurping and crunching sounds, he lights a lighter and sees people feeding on raw meat and the flesh of dead bodies; the man runs, opens a door and is impaled in the throat by two large tentacles, he thrashes, we see blood on his throat and we see him taking a bite from a dead woman's arm (he tugs at the flesh and we see blood in his mouth).
A man pokes a stick in a slimy creature slithering on the ground, it shoots a small spike into his chest, we see it wriggling its way inside his body, he falls to the ground writhing, and we see the thing wriggling inside him until it reaches his brain (his nose and ear begin to bleed).
A man is impaled in the abdomen by a tentacle, another tentacle tries to get in also, and the man grabs it and sticks it onto a propane tank where it is filled with gas.
A man spits green goo at a woman, she screams, she says "it burns," and her face begins to swell.
A slugman is stabbed with the pointed handle of a brush (he screams and bellows).
A tentacle is pulled out of a man's abdomen (we hear squishing and see green goo and blood seep from the wound).
A woman is flung against a wall, then into a bookcase by the large tentacles of the slugman.
A young woman is pinned behind a sofa when it is thrown at her by the slugman.
A large tentacle wraps around a woman's body and then releases her.
Three people are swarmed by large slugs and left covered with a clear slime, but otherwise uninjured.
A man is struck hard on the back by a man with a shovel; he falls to the ground, and shoots the other man in the foot (we see his bloody toes).
A young woman hides in a pick-up truck, a man, woman and two young girls who have been infected by the alien try to get in and get her, and the man pounds on the windshield with a large rock and it begins to break.
A young woman is chased by large slugs, she hides in a pick up truck and the slugs completely cover the truck.
A man fills plastic garbage bags with raw meat.
We see a sort of flashback sequence that shows alien beings battling other alien beings on alien planets.
On a TV nature show we see a crocodile snap at and grab a zebra.
A large slug slithers on the back of a deer.
We hear crunching and squishing sounds coming from a man, as he bends over in pain.
A man walks toward a dog and we hear the dog yelp (he presumably killed the dog).
People who have been attacked by the alien and become re-animated walk and act like zombies, and others who have been impregnated by the alien crave and eat raw meat.
Blood drips from an air vent in an office, a woman screams when she looks up and sees many large slugs streaming out of the vent.
A truck crashes into a car, re-animated people try to drag the passengers out of the car, and one man and one woman are taken away by them.
A huge rock falls through space, it reaches Earth's atmosphere, breaks in pieces and one piece crashes to the surface (we see a piece that has cracked open and there is throbbing red goo inside).
A man makes a comment about another man with a cleft palate.
A man picks his nose and wipes his finger on another man's hat.