The Planet Named Curiosity
The 999 passes the Curiosity Planet, a planet with a large red dot on it that makes the planet look like an eye. The Conductor orders the passengers to not stare at the planet, but one of the passengers, a young woman named Miiru whose boyfriend was pulled out of the train to the planet does. This enrages the planet, which sends its moons after the 999 and orders the passengers to come off. There they find Miiru's boyfriend. The planet demands that the Conductor remove his clothes, which he refuses. Tetsuro and Maetel do so instead so he doesn't have to. The planet then demands Maetel be cut open so it can see her insides. This enrages Tetsuro, who using a knife from Miiru's boyfriend cuts open the planet. Exposed, the planet is embarrassed and commits suicide after the 999 flies safely away.
Aired 06/03/1980EP 68 - The Planet Named Curiosity

Galaxy Express 999
After witnessing the death of his mother and being left for dead at the hands of Count Mecha, ten-year old Tetsuro Hoshino is awakened by a mysterious woman, Maetal. In exchange for only his company, Maetal offers him the ride of his life on the Galaxy Express 999. It is said that those who travel aboard the legendary train to the end of the line can receive a free mechanical body and with it, immortality.
Impoverished and alone, Tetsuro leaps at the opportunity and joins Maetal on a quest that will span the cosmos. As the Galaxy Express 999 makes its way across our solar system and beyond, Tetsuro is drawn deeper into a dangerous universe where peril lurks at every stop.
(Source: Discotek)