You're tasked with making World -1 an actual part of Mario's, uuh, lore. What role would you give it?

[Koopa con Carne]

An NPC in Super Paper Mario already suggests that "World -1" is a nickname for the underworld in Mario's universe, and while I find that idea intriguing, chances are high the dialog writers/localizers were merely jesting around with that line. Weeellll, now it's your chance to describe the infamous glitch as though it were an integral part of the Mario universe!

In the original Super Mario Bros. for NES, world -1 is simply a replica of World 7-2, an underwater level, that loops back to its beginning every time you reach the end pipe. In the Famicon Disk System version of the game, this level is still "coded" to be swimmable, but it takes place in an otherworldy setting where you can encounter Peach twice--inert, floating through the air with her eyeballs rolled up as though she were a ghostly figure--and Bowser--who is fighting to stay afloat at the area's event horizon. It is followed by Worlds -2 (a copy of one of the game's regular stages) and -3 (another glitched stage), then you're back at the title screen.

Give this thing a canon explanation will ya? (Hard Mode: try to avoid imagining it as some drug-induced trip.)

 

[Ray Trace]

Swimming? Nah that's not swimming, gravity is just turned off thanks to Bowser's Gravity Generator going haywire.

 

[SavK]

What if Bowser sabotaged the pipe so that when Mario goes through the wall the pipe secretly changes direction to a fake world made by Bowser to confuse him

Or the pipe breaks that works as well