Earlier this year, an earlier prototype for Pokémon Gold and Silver leaked in ROM form, and when The Cutting Room Floor got their hands on the file, they discovered dozens of unused Pokémon. These monsters were in development for the second generation games but were either scrapped altogether or heavily redesigned to become the Pokémon we all know and love.
Today a new batch of unused Pokémon surfaced, this time on a Japanese TV show called NHK. There aren't nearly as many scrapped monster ideas in this batch, and some of them are clearly predecessors of official Pokémon. The most interesting one is probably the early version of Scyther (the third creature on the top row), which almost looks closer to Charizard in appearance.