- The aliens are here
They're out in force tonight
The aliens are here
We better keep out of their sight
The aliens are here...
Directed by Jim Stenstrum, Scooby-Doo and the Alien Invaders is the third direct-to-video installment for the Scooby-Doo franchise, produced by Warner Bros. Animation with a Hanna-Barbera Cartoons, Inc. copyright. Like the two films before it, Mook DLE did the animation.
The gang is driving through the Sonoran Desert when a sandstorm comes up and Shaggy makes a wrong turn onto government property but only to lose control of the Mystery Machine when Shaggy sees an UFO and the gang find themselves on the outskirts of small town Roswell where people are supposedly being abducted by aliens. Its up to the gang to solve the mystery.
- Accidental Kiss: When Shaggy and Crystal kiss at the end of his daydream, Shaggy ended up kissing Scooby in real time, and he isn't too comfortable with it.
- Anal Probing: It is very subtly implied by Lester that probing was what the aliens who captured him did to him before letting him go.
- Babies Ever After: In the last part of Shaggy's daydream, he and Crystal have a son who looks just like Shaggy, aptly named "Shaggy Junior". Scooby and Amber also have a litter of puppies that look like Scooby, with some of them having Amber's fur color.
- Comically Missing the Point: Lester insists he has pictures of the aliens and their ship, but they turn out to be paintings, not photographs as implied. He again passes this along to the feds when the captured scientists insist the aliens were for real. The gang laughs knowing the feds will not be impressed by what they see. The best part is the scientists think this will get them off the hook, unaware of what Lester actually meant.
- Darker and Edgier: The atmosphere is grimmer than usual Scooby-Doo fare with the threat of aliens lurking in the background, the mystery of what the government is up to, and the quiet town is a pretty bleak setting. However, see Lighter and Softer.
- Did Not Get the Girl: Crystal and Amber are revealed to be aliens—they have to go back to their home planet at the end, and while they really like Shaggy and Scooby, they ultimately break it off, largely because they feel that a long-distance relationship wouldn't work.
- Disney Acid Sequence: "Groovy" is Shaggy and Scooby's idyllic, sweet as honey daydream about their love for Crystal and Amber, featuring them climbing mountains and borderline psychedelic imagery since both Shaggy and Crystal are hippie-age lovers.
- Embarrassing Hobby: Buck, a mechanic whom the gang consider a suspect, turns out to have been sneaking around to gather wildflowers. He didn't want anyone to know he collected pressed flowers because it didn't fit his tough-guy image.
- Exposed Extraterrestrials: When Crystal and Amber are revealed to be aliens, their true forms do not appear to have clothes.
- Foreshadowing: Aside from being just a tad out of touch with the times, it's obvious that none of Crystal's gear is of human origin, a clue early on that she and Amber are not of this world.
- Fourth Date Marriage: Shaggy gets a song about his new fantasy of marrying Crystal, having children with her, and all that jazz within a few hours after meeting her.
- Interspecies Romance: Shaggy and Crystal along with Scooby and Amber because they're aliens.
- Laser-Guided Karma: Just as Scooby is about to wolf down a burger Lester knocked to the floor by accident, Shaggy downs it in one gulp. After years of stealing Shaggy's food, it's refreshing to see Shaggy beat him to the punch.
- Lighter and Softer: In spite of the grimmer atmosphere, it has the real aliens as the good guys and disguised humans as the bad guys.
- Mythology Gag:
- During Shaggy's song, and the subsequent daydream, there's a brief part that shows the rest of the gang in their original series outfits as they're all chasing a ghost in an old house. They even subtly throw in the original HB running and stopping sound effects from the 60s and 70s underneath the music. That's some attention to detail right there.
- During the song, Shaggy also mentions that he and Crystal would buy stuff from 1969, the year the original cartoon Scooby-Doo, Where Are You! originally premiered.
- New-Age Retro Hippie: Crystal the photographer is one. Or so it seems, until it's revealed that she's an Alien Among Us.
- OOC Is Serious Business: After Shaggy and Scooby meet up with the others at the town's local diner, they're still so lovestruck after Crystal and her dog, Amber, that when their friends ask what they want to order, the two Big Eaters say they aren't hungry and don't even order anything. Fred even grabs Shaggy's water bottle and sniffs it, apparently checking for booze.
- "Scooby-Doo" Hoax: Zig-zagged. The very human villains faked the main alien threat, while the actual aliens are disguised as humans.
- She's Got Legs: Local waitress Dottie isn't bad looking, and we get a lengthy shot of her legs from behind as she walks away.
- Star-Crossed Lovers: A non-lethal version. Shaggy and Crystal along with Scooby and Amber have to part ways at the end.
- Suddenly Speaking: Crystal's dog Amber turns out to be able to speak shortly after the gang learn of the pair's true nature of being aliens.
- Talking Animal: Amber is revealed to be one at the end while in her dog form, much to the surprise of the gang. Fred comments on the irony, seeing how Scooby already fits the bill.
- Totally Radical: Crystal's even worse than Shaggy, seeming like she was plucked right out of the 1960's. Turns out her race discovered TV and radio transmissions from Earth in the 1960's and simply assumed that everyone still talked and dressed like that.
- Tsundere: Crystal's dog Amber was this to Scooby when Shaggy and Scooby met the girls, being aloof and dismissive toward him when he tries to show affection. She does eventually come to like him over time.
- Unmanly Secret: The gang is suspicious about the mechanic who's supposed to be fixing the Mystery Machine as he's extremely rude towards them and very secretive, and they find him alone out in the desert when he's supposed to be working on the van. He ends up being a Red Herring, but they're still curious as to what he was doing in the desert, so they decide to ask. Reluctantly, he reveals that he's been collecting and pressing wild desert flowers. He then explains he doesn't like to tell people about it because if they find out he has a soft side, they would walk all over him.
- Wrong Turn at Albuquerque: Shaggy makes a wrong turn onto government property courtesy of a sandstorm and then winds the gang up near Roswell after seeing an UFO.