Goof: At least twice in this episode, Lance's uniform color is seen as red instead of blue.
Even though this special aired last, it chronologically should precede the first episode of Season 3. The main keys are that Merla is not seen or spoken of, and that Cossack runs in fear in the last episode of the show while he shows no signs of cowardice in the Fleet of Doom special. Another piece of support is that Haggar can make herself beautiful in the episode about the Cadmium Flower but no one knows it, though she is seen later doing the same in part of the Fleet of Doom special (though the glamour is different).
Who's on first is probably a take off from the famous Abbot and Castello's "who's on first" skit.
The first time Prince Lotor's harem is seen, they are all beautiful women with blond hair, explaining Lotor's obsession with Princess Allura. However, this time when his harem is shown, they all have different colors of hair.
Goof: Twice they miscolor voltron's right leg yellow. So they both appear as being yellow, when the rest of the time they're the proper coloring.
Goof: At least twice Keith gives orders to red lion, but mistakenly says Hunk, when Lance is the pilot of red lion.
Goof: At one point while they're fighting underwater Keith's uniform is black.
Goof: When they go out to the lions you can see them going through the lava/water/etc but the lions take off from the castle instead of their hiding places.
When Allura talks to the mountain man Runan in Voltron, she is told that he used his mental powers to call forth a starfleet from another dimension to transport them away to where even Zarkon could not reach them, and that they pretended mother and son are buried there when he shows her the fake grave. The idea of multiple dimensions is carried forward into Voltron: The Third Dimension; the idea of mental powers playing a strong role in the universe continues through the character of Merla in the second season of Voltron: Defender of the Universe.
When it's time to use the Blazing Sword, rather then Keith saying "Form Blazing Sword", he simply says "Blazing Sword", and the Blazing Sword is simply there in Voltron's hand, rather then being formed, as usual, by putting the two hands together and forming it around them.
After the giant robot fires it's Metal Piercing Rockets, three of them punch through the head (Voltron's right foot) of the Princess's Blue Lion (Voltron's right leg), one through the nose, right eye, and forehead, and through her interior glass viewscreen. However, after Voltron falls out of control, when Kieth gets it back under control, the three Metal Piercing Rockets are gone, and there is no damage showing they were ever there, inside or outside.
Even though the Yellow Lion lost it's front left paw after firing it's Rip Claw at the enemy robot, the paw crushed in it's hand, and later images showing the Yellow Lion without the paw, when the Lions merge to form Voltron, the missing paw is shown on the Yellow Lion.
When talking, the team seated around the table, the far shot of everyone shows the princess in a white outfit with a pink collar, like her Voltron uniform. However, on her close up, it is shown to be her pink outfit with the white collar that she wears around the castle.
We learn in this episode Allura cannot be crowned Queen until she marries (chooses a Prince Consort). Considering that the first ruler of Arus was in fact a woman according to the sequel series, Voltron: The Third Dimension, this is an interesting thing to note.
Keith and the rest of the Voltron Force catches on to Planet Doom's scam relatively quickly, based on their experience with Witch Haggar's spells and Lotor's obsession with Allura. Ironically, in the original GoLion episode this is based on, Kogane (Black Lion Pilot/Leader) and the GoLion Team fail to catch on until they see the lengths their enemies Honerva and Sincline (Witch and Prince) are willing to go to get the supposedly dead body of Farla (Princess). Usually, the darker tone of the original anime means that the heroes of GoLion are more savvy than their Voltron Force counterparts.
The first episode where they say "Let's Go Voltron Force!" when they form voltron. Previously they just dubbed it "Voltron!" and on one occurance "Go Voltron Force!"
Goof: Keith is supposed to be going to blue lion, but they show him going to black lion.
There is, apparently, an edit for violence in this episode's finale battle. Just before Voltron forms the Blazing Sword, Yurak got hit by some Proton Missiles and then fires lasers from his finger tips at Voltron. After the sword is formed, in the next sequence, there's a gaping hole in Yurak's stomach. This wound is not where the Proton Missiles struck him.
When Hunk finds Twila she is in a brown slave dress, when she wakes up in the infirmary she is in a white and blue dress. After she tells Allura and the Voltron members how she escaped from Planet Doom her outfit changes from the slave outfit to the blue and white dress several times in the next shots.
In the previous episode the four male Voltron members all had their own rooms that they slept in. In this episode they are all sharing one big room to sleep in.