Walk through walls glitch

The walk through walls glitch, also known as the staircase glitch, is a glitch in EarthBound allowing players to walk through walls, as the name implies. This glitch allows the player to go practically anywhere on the map.

Cause
The game does not treat movement on stairs the way movement is treated normally, instead all imput is disabled and the player keeps walking automatically until the player is off the stairs. If an interruption occurs while on the stairs, such as a phone call or critical health warning, the player stops walking and control imput is re-enabled. This puts the player in a "ghosted state" which allows the player to walk through any solid object. The glitch cannot be triggered with escalators or by walking off the stairs.

Performing the glitch
There are two methods to activating the glitch:

First method
The easiest method is to let a party member get a status ailment that slowly drains their HP (such as poison or sunstroke) and allow their HP to get low enough to get a warning that the player is at low health, the player needs to be walking on the stairs when the message appears. The timing window differs between the top and bottom of the stairs and also depends on where along the width of the stairs you are. Walking onto the top of the stairs from the upper side of the stairs's width, the timing window is about 15 frames. Walking onto the bottom of the stairs from the upper side of the stairs's width, the timing window is about 8 frames. Starting from the lower side of the stairs's width reduces the timing window by a few frames. If done correctly within the window, the party regains full control and is able to walk freely anywhere on the map. However, if the interruption occurs a few frames too late, the party is able to walk through walls but is restricted to walking diagonally with no way to escape the diagnal movement.

There is a limitation to this method: there os an infinitely long horizontal line at the location the glitch is triggered. If the player tries to cross this line, the game will warp the party onto the stairs no matter where the line is crossed, and the party can end up stuck on the stairs. If the glitch is triggered at the top of the stairs, the line is actually a bit below the party; conversely, if the glitch is triggered at the bottom of the stairs, the line is slightly above the party. Hence, if the player want to travel up or down, the glitch needs to be triggered at the top or the bottom of a set of stairs respectively.

Second method
1. Walk onto a set of stairs.

2. Get the entire party wiped out while on the stairs. This can be done by having all party members unconscious except for one person.

3. That person should have a health-draining status effect such as poison.

4. Return to the title screen from the game over scene. This can be done by answering "no" and then "yes" at the prompts. Resetting the game will not work.

5. Open a different save file.

The party will start in a ghosted state upon loading the save. Unlike the first method, there is no horizontal line that the player cannot cross.

Exploring the map
As noted prior the player can walk through any solid object on the map, although the player cannot interact with any NPC or object. While exploring, if the party enters another location, the game loads the music but does not load the tileset in the area, and the player appears to be walking in a black void. (Some rooms share the same tileset, and entering one of these rooms will load every room with the same set. You normally can't see more than one of these rooms at a time because they are never next to each other.)

When the player enters an unloaded location, there are two ways to load it: using the map or the Sound Stone. The map is faster but can be used only in towns, while the Sound Stone can be used anywhere but disappears after defeating Ness's Nightmare.

With an area loades, the glitch can be deactivated by either entering a door, falling through a hole, or walking onto stairs or an escalator. There is a catch, however: if the glitch was activated using the first method, entering a door or hole that leads to a location on the other side of the invisible horizontal line will cause the game to try to warp the player onto the stairs and likely cause the party to get stuck.

An interesting outcome that can be triggered using this glitch is if the player goes to a part of the map that triggers an event that was in a previous part of the story and deactivates the glitch, the game start the event even though it was already completed, thus putting the player in that part of the story that was already completed and causing them to replay the game from that part of the story. One way to trigger this is to deactivate the glitch while in Moonside and defeating the Evil Mani Mani, this triggers the scene where the player is in the Cafe warehouse, forcing the player to replay the story from that point.

Finishing the game
Although it's possible to go straight to Giygas in this state, the game will soft lock during the first prayer scene. This is because each area that appears in the prayers needs to be "prepared" to run the scenes. This preparation occurs when the party travels back in time with the Phase Distorter.

Two events are required to initiate the Phase Distorter quest in Saturn Valley:

1. In Lumine Hall, fall through the hole leading to the Lost Underworld: this causes Dr. Andonuts to appear in Saturn Valley.

2. Defeat Ness's Nightmare: this causes the Phase Distorter to appear.