From Bulbapedia, the community-driven Pokémon encyclopedia.
B óË ÁN is a glitch Pokémon found by using the "Always Your Turn" code on FireRed and switching Pokémon. This glitch causes the game to stop (except for the movement of the sprite), and no action can be taken (except accessing the Help menu).
When encountered, it will continuously scroll from bottom to top, and sometimes flip over (causing a small green distortion). It only appears as a yellow/orange square and cannot be found in any other way for the moment, not even by hacking the game's code.