Okay, I've discovered an insane walk-through-walls glitch, and I've reproduced it. Let's hope that ZSNES v1.42 is accurate compared to other emulators.
It involves two things:
1) If someone is taking damage out of battle (poisons, nausia, sunstroke, cold, or wading through Deep Darkness), and the character's HP drops to "critical" (about 25% of max HP), a message will appear.
2) When your party walks straight onto a downward staircase, the lead character will "catch" before starting the diagonal walking.
Combine the two: Time it so that a poisoned/etc. character prompts the critical message to display just as the lead character "catches" on the diagonal-downward path of the staircase.
The result? After clearing the critical-HP message, your party will now be able to walk anywhere, all the while always facing the same direction. You can restore physical contact with the world by entering a door/cave/some other path/warp.
I discovered this on accident while exploring the pyriamids. Looking at a map (
http://starmen.net/mother2/maps/fullmap_small.png), I went completely north until I reached Giygas's lair, entered & exited the place (my party turned into robots in the process), and fought him.
Unfortunately, during the first prayer cutscene, the normal Saturn Valley music played, and the game stalled after the miner went to greet Dr. Andronuts. I guess a flag hadn't been set yet.
So, if this trick were used, we'd probably have to jump right to Ness's Nightmare or where Poo learns Starstorm omega. Still, a huge chunk of the game would be cut out.
I'm guessing that the earliest we could do this would be at the stairs in the underground passage in Threed. So we could maybe skip Poo.
Please tell me this wouldn't obsolete the current run.