Fireball XL5

The Doomed Planet (1x2)

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The Fireball XL5 narrowly misses a planet that has broken out of it's orbit and they realize the planet is on a collision course for the planet, Membrono. After concluding the planets are uninhabited, Steve realizes he saw a flying saucer. After the ship lands at Venus' house, the XL5 is lured back to save the planet Membrono from destruction.