It is found in Pokémon Yellow by doing Method #3 of the Mew glitch with a Pokémon with a special stat of 195. Its Red/Blue equivalent is h POKé. However, since h POKé's Pokédex entry freezes the game, some players might want to trade a ゥ ( Z4 in order to get h POKé.
This glitch Pokémon article is part of Project GlitchDex, a Bulbapedia project that aims to write comprehensive articles on glitches in the Pokémon games.
Trivia
ゥ ( Z4 uses the bug symbol when seen on the Party screen, due to it being a hybrid of Beedrill.
ゥ ( Z4 evolves into Squirtle, despite being a hybrid of Beedrill.