Exodus is the first episode of ThunderCats.
With their home planet, Thundera, about to explode, the Thunderians flee to a distant galaxy. Before they can make the long journey, the Mutants sweep in and destroy most of the fleet in an attempt to capture the Eye of Thundera, and a battle ensues.
A distant planet is collapsing and about to explode. The Thundercats (Thunderian nobles) and the rest of the Thunderian commoners must find a new home just after their home planet, Thundera, explodes. The Thundercats flagship had already safely left and is now traveling in outer space when an enemy known as the Mutants attack and leaves their ship severely crippled. A young boy named Lion-O must learn what it means to become a man and Lord of the ThunderCats as he learns to wield the power of the Sword of Omens.
Accompanied by the Nobles of Thundera, the leader of the ThunderCats Jaga, and his nurse maid, Snarf, Lion-O escapes the planet's destruction. After acquiring the Sword of Omens, the ship is attacked by mutants from their home world. During the battle, the Mutants try to get onto the ThunderCats' ship to take the Eye of Thundera, a powerful relic that is passed down from generation to generation of leaders of the ThunderCats. Little do the mutants know, the Nobles are willing to die for their leader and the Eye of Thundera.
The Mutants are beaten back, but with a cost to the ThunderCats: Jaga is left to pilot the ship due to a short to the navigation system (autopilot was normally used when flying at lightspeed) while it is in hyperspace. While the rest are in age-slowing sleep chambers , he makes do with what he can, and sets the ship on autopilot when he is no longer able to pilot it. He programs the computers to wake the remaining ThunderCats when they are about to arrive at the planet, and sets the ship on a crash course for the world that will be known as Third Earth.
There again, the ThunderCats must face some of their old enemies, the Mutants, led by Slithe and, due to surprise of all, Lion-O is now a grown-up ThunderCat. His sleep-chamber was damaged and his body grew many years older while the others remained in suspended animation. He is now no longer a Thunderkitten and instead, is in an adult body like the nobles that he must now lead in battle despite still having the mind of a child and lacking the experiences that would make him a good leader.
- Lion-O in a scene talking with Jaga being shown the sword loses his mouth briefly.
- This episode is contradicted frequently later in the series:
- Development work on ThunderCats began in 1983, with the script for this episode being produced in 1984, but the series did not make it to air until 23 January 1985.
- This is one of the few times that the ThunderCats aren't wearing uniforms.
- Unlike the rest of the ThunderCats, Jaga has brown eyes, while the other seven ThunderCats have orange eyes.
- Jaga's death scene resembles that of Jedi Master Yoda from the film Star Wars. Like Yoda his body seemingly vanishes when he died, leaving only his robes behind. Later, they both appear as a spirit to the hero.
- “Exodus” was initially broadcast as part of a feature-length pilot, featuring this episode and The Unholy Alliance, cut together to create a one-hour special. When released on home video as Exodus: The Movie, the episodes “Exodus” and “The Unholy Alliance” were joined by edited versions of the episodes Berbils and The Slaves of Castle Plun-darr, all cut together to create a “movie” version of the first four episodes.
- The first broadcast of Exodus and the home video release both contained a special 1 minute 45 second introductory sequence, introducing the audience to the series’ main characters and to the concept. This "Lost Intro" has never been officially released and is absent from the stand-alone episode of Exodus on the ThunderCats DVD.
- Cub Lion-O: Aw, I don't want to be safe! Safe is boring!
- Tygra: And a fine figure of a ThunderCat you've grown up to be, Lion-O.
- Cheetara: And so handsome, too.
- Lion-O: We will survive and create a mighty new empire. I, Lion-O, Lord of the ThunderCats proclaim it.
- (Holds up sword as the Eye of Thundera opens, then looks around at the others)
- Lion-O: Uh, with your help, of course.