The Cable Club Glitch City transition
The Cable Club Glitch City transition is a natural glitch in Pokémon Yellow and possibly other Generation I games such as Pokémon Red and Blue.
When entering the Cable Club Trade Center (and Colosseum?) the player has a chance of seeing a Glitch City for a split second before the room fully loads.
The left and right halves of the room may appear on the right and left sides of the screen respectively and glitchy tiles appear in between.