Going up and down the stairs infinitely glitch
The going up and down the stairs infinitely glitch, also known as the footing glitch, can occur as a glitch derivative of the Trainer escape glitch.
This glitch causes the player to automatically go up and down stairs (warping them between two maps) infinitely.
Steps and requirements
You must have not saved Silph Co, but Silph Co. must not be blocked. In Red/Blue, you can probably use a "Rival's effect" (or 'Jack effect', etc.) glitch item (e.g. NEW NAME (hex:B1)) to go through the Rocket, however. You must have access to Saffron City.
1) Set your Escape Rope location to Saffron City.
2) Go into Silph Co., then go to the fifth floor. Do a Trainer escape glitch (long-range Trainer glitch) with the Juggler there via Escape Rope. You can also do a Trainer-Fly with the southern-most Rocket on 8F.
3) You'll go to Saffron City. Go back into Silph Co. and battle a Rocket that walks up to you (2F and 8F work).
4) Go back to 5F (or 8F) via the stairs, and the start menu will open (if the last text box was the start menu). Close it, and you'll go up and down the stairs infinitely.
This glitch probably works in other locations accessible by stairs if you use a Jack-Fly.
Saving after the start menu appears, may cause the Start menu to pop up again after resuming the save, but stop this glitch.
Attribution
Settcënko, LanceAndMissingNo., WikiDex, ChickasaurusGL (this article's text)