In the first-season Voltron Legendary Defender episode “Taking Flight,” the Castle of Lions tears itself from the surface of the planet Arus, and assumes what became its ongoing new form: a spacecraft. Its crew informally called it the “Castle-ship.”
Voltron Legendary Defender wasn’t the Voltron-related program with a Castle-turned-spaceship.
In Beast King Golion, one of the anime programs that were adapted into Voltron: Defender of the Universe, the Golion Team calls Castle Gradam its home. In the 50th episode, “The Great Storming of Galra,” Raible reveals that the Castle can convert to a spaceship. The Golion Team uses the ship as part of a final assault on the planet Galra.
The Castle’s transformation initiates when Raible inserts a special key into the Castle’s main console.
The Castle does not launch from Altea until Golion‘s 52nd and final episode, “Burn Galra Castle.”
Because Golion‘s 52 episodes were adapted into episodes of Voltron: Defender of the Universe, Castle Gradam and its ship mode appear in Voltron, although in the latter program the Castle is called the Castle of Lions. In Voltron, the Castle’s ship mode is revealed in “Zarkon Becomes a Robeast,” which was adapted from Golion‘s “The Great Storming of Galra.”
The Castle of Lions’ ship mode makes a notable reappearance in “Fleet of Doom,” the two-part final story that was animated entirely new for Voltron. In that story, the Castle of Lions transports the Lions to the Galaxy Alliance’s Power Base, to rendezvous with the Voltron Vehicle Team and remove the Drule/Doom forces that threatened the base.
Although Voltron: The Third Dimension featured a Castle of Lions, no ship mode is seen or referenced in the program’s 26 episodes. Perhaps a ship mode would have been revealed had more episodes been produced.
In the 26th and final episode of Voltron Force, the spirit of King Alfor activates the Castle of Lions’ transformation to its spaceship mode. The Castle’s ship mode is a surprise even to Princess Allura. The Castle helps Voltron win a decisive victory over Maahox.
Castles-turned-spacecraft are seemingly as much a part of Voltron lore as the Defenders of the Universe themselves.