Parasites are parasites. They look like a bug, fly or worm and can be found in many types of films. When they show up in a movie, it becomes quite difficult to guess what type of parasite they actually are.
However, in the movie Aliens, there was an Alien Bug parasite. The parasite infected Ripley, played by Sigourney Weaver, and caused her to transform into the "Queen". She created a gigantic queen cyst, then blew it up in order to kill it.
In the movie, Resident Evil, there was also a spider, which was an element of the character, Chris Redfield. It is not very clear if this spider parasite infected him. In some cases, the parasites may be the enemy or simply camouflage.
There are a lot of movies with parasites, but they do not always die and stay dead. For example, in Spiderman (movie), the arachnid known as the crab symbiote, which appeared only for a moment and was killed by Peter Parker. It did not have a particularly impressive body, except that it had a lot of legs.
Parasites are very common in the movies. There are a lot of movies that depict their presence without any details. In addition, many movie parasites were really a misnomer; many parasites are alive, but in some cases, they were merely camouflage for the main character.
In the movie, the Spiderman cyst had a web and could crawl out of its host. But it would not release the spider directly from its host because it was going to create more hosts.
In the movie, the alien killer was a parasite that would disguise itself as a real organism to attack humans and infect them. It also produced more parasites that were released into the environment to attack other organisms.
Most of the parasites in movies that seem to be just a type of animal. Some of them are similar to parasites, such as the parasitic wasp in the movie, The Mummy. Other parasites are completely alien, and so it is a bit difficult to classify them.