From the Super Mario Wiki
Outer Space is the setting of Chapter 4 in Super Paper Mario. Chapter 4 may not take place in the outer space above the Mushroom Kingdom, but rather that of another dimension. It was once the location of the Squirpia kingdom. Upon arriving to Outer Space, the heroes realize they are unable to breathe, which forces them to return to Flipside to try to find a Space Helmet. After taking notice of the fishbowl Merlon gave to Pook, Mario asks for permission to use the bowl as helmet. Pook agrees to this, but only after the heroes find Captain Gills, who was already too big for the fishbowl, a nearby place to live. After setting Captain Gills free in the canal on the basement floor of Flipside, the heroes proceed to Outer Space.
In Chapter 4-1, the heroes meet Squirps, a mysterious alien creature who functions as a ray gun for stages 4-1 and 4-3, as well as in the battle against Brobot. A large portion of this chapter involves a Squarp Hole maze, which requires the player to remember which Holes are linked to which in order to progress.
Chapter 4-1: In Outer Space
As soon as the the team move into the Green door they find themselves in outer space. Tippi takes them back to Flipside, and they need to find a Space Helmet to continue. When they find the helmet, they come back into the door. The main thing is the warp hole maze that they need to find the way through to complete the chapter.
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