It is only obtainable via the Johto guard glitch with Marill. It is unobtainable via the Mew or Ditto glitch, due to Tamer appearing.
It will become a -PkMn if traded to Pokémon Red and Blue. It evolves into Q◣ at level 6. Notably, it uses three cries - Rhydon's in summary, Zapdos's when entering battle and evolving, and Mankey's when fainting.
also has a glitch screen, particularly the blackout variant.
This glitch Pokémon article is part of Project GlitchDex, a Bulbapedia project that aims to write comprehensive articles on glitches in the Pokémon games.