While I think it's neat to see what else they had stashed in the code, I believe the fact that you can't get there through any in-game means and the guy having to really work at patching the game to allow for such a thing to happen really disqualifies it as truly being a "minus world." With enough coding and patching, you could probably make it so the in-game character in tons of titles can run through whatever random, "garbage" code is loaded elsewhere in memory/ROM--that doesn't make it comparable to what happened with the SMB minus world.
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Need Stadium Events + Panesian titles, 6-in-1's, Menace Beach, Moon Ranger & Secret Scout to complete my licensed/unlicensed sets.
If you've got any of the above for sale, hit me up!