For those who are familiar with Joseph Lai's body of work, this is Thunder Prince IN SPACE. A Humongous Mecha pseudo-anime released in 1991 about three children that can pilot giant robots trying to defeat the Big Bad and his army: the Dark Empire. There are also some Space Opera elements thrown in with advanced space stations and dogfights going on in space.

This decidedly weird animated film is a result of Joseph Lai buying South Korean cartoons on the cheap and editing them to make "new" features. The result is a Frankenslation after putting all the different shows together.

The film was edited with footage from Savior of the Earth (not a ripoff of mecha anime, but instead the movie TRON), Defenders of Space - Phoenix-bot Phoenix King, King Robot, Protectors of Universe - Super Express Mazinger 7, Solar Adventure, Space Transformers - Micro-Commando Diatron-5, Super Mazinger 3 and Iron Man Trio. All of the aforementioned movies are also ripoffs of other anime like Mazinger Z, and even robot cartoons that gained fame in America, like Transformers, Voltron, and even Mighty Orbots (and all but the last were separately dubbed by Joseph Lai as well).

Has nothing to do with UFO Robo Grendizer's Finishing Move.

This film provides examples of:

• Aborted Arc: A lot of these, thanks to it being stitched together from pieces of around 9-10 totally unrelated movies. Lots of threats are set up but never paid off, because the resolutions weren't among the parts that were brought over from the original series.
• All There in the Manual: The back of the cover describes the entire movie from start to finish, including a plot about saving a scientist. None of this is apparent in the film itself due to the haphazard editing.
• Child Soldiers: The main characters, since the movies being incorporated were ripped off from anime where kids or teenagers piloted mecha against alien invaders.
• Compilation Movie: As noted, it was made by splicing together bits from a plethora of other Korean knockoff anime.
• Covers Always Lie: None of the characters on the cover match any of the characters seen in the film, rather being original designs.
• Decoy Protagonist: It's never actually stated in the film which of the teams seen in the film are the Space Thunder Kids.
• Epic Flail: Some of the giant robots of the Dark Emperor fight with these in space, Newton's laws be damned.
• Frankenslation: It combines no less than seven different Korean cartoons.
• Inexplicably Identical Individuals: The lines of civilians running away from the buildings being leveled by Neon Light Godzilla.
• No Celebrities Were Harmed: Kim Il-sung, as the evil general working with the aliens. A lot of the incorporated movies had villains who were thinly-veiled analogues of the North Korean military, but the movie that character came from (Solar Adventure) was especially blatant.
• Random Events Plot: Due to the film being somewhat haphazardly cobbled together from a bunch of other films, there is a lot of jumping between several completely unrelated plot points with only token attempts at telling some sort of overarching story with them.
• Recycled Animation: Taken to a whole new level with this film. The animation of the entire film was taken from several other Korean cartoons and stitched together into one big thing.
• Space Is an Ocean: Speeds are called out in knots. Not even hundreds or thousands of knots, as would be the case for spaceships if they didn't just use MpH/KpH to begin with, but tens of knots, as if they were going at nautical speeds. Other parts have passingly realistic space motion.
• Strong Family Resemblance: Inverted doesn't even begin to describe it. Apparently the seven foot tall one eyed blonde space pirate badass vixen has a sister who is a one foot tall robot pig creature named Sandy. ^note  It isn't explained any better in the movie that part comes from, Savior of the Earth.
• What Happened to the Mouse?: The space station that was attacked by the meteors at the beginning was never seen again.