As Corman-produced Alien knock-offs go, this is considerably more coherent and somewhat less fun than Galaxy of Terror, but it does have an American Gladiator faking a seizure, Roddy McDowall wrestling a rubber worm, and William Shatner's daughter smoking dudes with a flamethrower.

Wasted time the weekend before the Oscars watching this silly Alien/The Thing knock-off. But, with Planet of the Apes star Roddy McDowall leading the way. And giving some much needed gravitas to the proceedings. Love how committed he is to something that clearly doesn’t deserve him. He even has an interesting backstory that would eventually echo the basic plot of 28 Days Later.

Rip-off of Ridley Scott's Alien taking place under the sea. There's even an explicit "homage" to Alien: the submarine's computer password is NOSTROMO.

It's a good rip-off. Roger Corman is the executive producer, so you can expect a fairly good B movie.

I have an idea! Let’s take “The Thing”
And put it under water!

This is a cheap but entertaining knock-off of THE THING and ALIEN, produced by Roger Corman.

A crew stationed on an undersea base receive a distress signal from a nearby Russian base, so they go to investigate. They end up returning with remnants of an ancient alien parasite that starts to infect the crew, leading to paranoia and suspicion about who is or isn't infected.

Yes, you get it, it's a blatant THE THING rip off, but it's still okay, as the characters aren't too bad and the actors all seem to be into it. Roddy McDowell gives a decent performance here as the chief medical officer, and the rest of the cast are good enough to make the whole thing watchable and enjoyable in it's own way.

"Uknown Origin" (also known as "The Alien Within") is an "Alien" knockoff that has the good sense to also borrow liberally from "The Thing" and "The Abyss" or "Leviathan." This pastiche of plagiarism could easily be written off due to its low-rent production value, utter lack of originality, and cast of dubious performers. Thanks to its Corman/New Horizons/Concorde-related pedigree, however, the experience is not that bad.

In the not-too-far-off future, the crew of a deep-sea vessel discovers a parastic creature that moves crewmember to crewmember. The bulk of the story is concerned with discovering who's infected and who isn't, and the plot moves through its recycled beats with at least a modicum of entertainment value. The whole thing is watchable for what it is, and, though it offers no surprises, it does offer a small amount of sci-fi/horror fun.

Put Alien and The Thing into a blender with a dash of Roddy McDowall and you get this movie. It's pretty cheap and not great, but it gets the job done. McDowall as the doctor is certainly the best reason to watch it. He's honestly pretty decent.

The rest is just derivative, but does a pretty decent job of it.

A low budget rip on Aliens and The Thing set at the bottom of the ocean.

Has all the standard pieces.

Jumpy crew.
Claustrophobic setting.
Android.

Unoriginal but never dreadful.

Stupid Roger Corman knockoff of The Thing and Alien, but it’s mindless and fun to watch if you’re a Roddy fan. He’s got the best role of the whole movie obviously, and he makes the absolute most of it. When Roddy starts to use his soft, sort of whiny, voice when he’s talking to you, you know shit’s about to go down.

Oh my dear Catherine. Don’t you sometimes think that God has a sick sense of humor?

It is a sort of Alien and The Thing combined ripoff with sub par effects, not much suspense build up, and quite a bit of bland dialogue. It makes the writing in Event Horizon (another semi ripoff) look well done. It’s not intolerable though. And I at least enjoyed this to an extent (I can’t say the same about Event Horizon).

Roddy McDowall stands out as, apparently, the only one giving a shit about this film and putting all the work he can into his performance. It’s worth it to see what he was able to wield in character development with a weak script, I truly enjoyed the movie overall during the moments when he was on screen. He’s still brilliant here.

After years of plagiarizing ALIEN, Corman decided to do it again! Only this time Carpenter’s THE THING gets thrown into the rip-off blender. Toss in a sprinkle of Roddy McDowall, some of the cheapest production design ever, and multiple stunt performers running around in flames and THE ALIEN WITHIN delivers on its most basic of B-movie Saturday Matinee aspirations.

As far as “combined Alien/The Thing knockoffs set underwater” go, this is pretty much a perfect baseline - not quite as transcendent as Leviathan, but still rock-solid B-grade sci-fi horror that’s out and done in under 90 minutes. Every set in this looks like the one exhibit at your local science museum that hasn’t been updated since the early 90s.