"Mission to the Sun" is part two of the fifth episode in the two season of Courage the Cowardly Dog, written by David Steven Cohen, which aired February 22, 2001," following "Human Habitrail." It is the eighteenth and a half airing and thirty-sixth episode overall.
In this episode, Courage brings Muriel the mail which reads that the Bagges have been offered a time-share as long as they "go on a little trip." We then find them upon a spaceship heading towards the Sun. After Eustace turned the main computer on, they are briefed by The General speaking gibberish and the ship's computer that the sun is going out and that they need to fix it using the tools kept inside a briefcase.
Meanwhile a space worm infiltrates the ship and gets inside Muriel's brain so he can take control of it, making her do crazy things to herself and Eustace during meal time. While Eustace accidentally drops his hat down a space toilet, and is forced to go outside the ship to retrieve it, the space worm breaks a control in Muriel's brain making her AWOL! She bites through the ship's electric wires shutting the ship's computer down, then biting through an air pipe which was the only thing connecting Eustace to the ship thereby sending him drifting of into deep space.
Courage then confronts Muriel and learns the identity behind who's controlling her brain: Mustafa al Bacterius. He and his kind like it dark and don't care if the sun goes out. Courage tries to extract the space worm out, but Muriel takes the plunger he was using and is sent hurling towards the ship's toilet, with her head getting caught. The suction power of the toilet forces Mustafa out of Muriel's head, and into the vastness of space.
Courage manages to get a normal Muriel's head out of the toilet. The ship then lands on the sun, and Courage thinking quickly remembers the briefcase and runs down a stairway and a passage to the sun's core, meanwhile the ship begins to melt, leaving Muriel to frantically dance on the sun's surface. Courage comes to the core of the sun to find a light bulb flickering dimmer, Courage opens the briefcase to reveal another light bulb inside, Courage untwists the sun's light bulb turning everything dark then replaces it with the new light bulb causing the sun to burn brightly again. Courage and Muriel now wonder how they are going to escape the blazing inferno as they frantically jump up and down, their prayers are answered they see Eustace riding an asteroid, Courage fires an anchor from his spacesuit, lashing onto the passing asteroid.
It is then revealed that the time-share offered is on planet Mars, and the organization have even sent the Bagges' house there, shortly after Eustace behaves strangely, and the episode ends with us seeing that Mustafa has returned; this time, in Eustace's brain.
- This episode marks the only time Courage interacts with a computer whilst not in the farmhouse. Incidentally, the computer's voice is the same as Courage's computer.
- This is the second consecutive time that Muriel goes bald, the first being Human Habitrail, which was the previous episode, this time it was caused by Mustafa al Bacterius controlling her nervous system.
- Mustafa al Bacterius looks a lot like the Hard Drive Virus from "Hard Drive Courage," and they both share the same voice actor(s) (both in English and in Japanese.)
- The music used in this episode is the Blue Danube, made famous by 2001: A Space Odyssey. The piece was also used in the SpongeBob SquarePants episodes "Jellyfishing" and "Squidward in Clarinetland."
- This episode shares its music with Heads of Beef.