Unreleased Pokémon Surfaced From Gold And Silver Demo

Fans at The Cutting Room Floor have found a mound of unused sprites for Pokémon Gold and Silver in the demo for these versions back in 1997.
When revisited by a random user who posted a ROM of the demo, fans were able to discover some early versions of known Pokémon and of some that never made it into any of the titles. The user posted two debugged and nondebug versions of both Pokémon Silver and Gold.
Some never used Pokémon like Flambear, Volbear, Dynobear, Cruz, Aqua and Aquaria present in ROM. These were substitutes to Cyndaquil and Totodile before they were created with their evolutions.

By a user on RestEra, The Shadow Knight, has composed a image of every sprite in the demo.

According to IGN, there’s also unused second generation Pokémon included in the image as well.
Source: The Cutting Room Floor