Unlicensed Pokémon content

The unlicensed Pokémon content include both unauthorised Pokémon cameos in other games and Pokémon-like characters created to avoid lawsuits.

Examples

In the video game "Catherine" is an unused possibly unlicensed remix of Pokémon Diamond and Pearl's wild Pokémon theme called "poke_btl_loop"
In Dragon Quest Monsters 2 are possibly unlicensed tokusatsu/kaijuu inspired Pokémon sprites, featuring Pikachu
The Rocket Company game Nashi-jiru Busha! Funassyi VS Dragons contains possible unused Pokémon menu sprites; of Pokémon Pichu, Chespin, Fennekin, Dedenne, and Diancie.
Serebii.net used to have a section, detailing unofficial, false Pokémon spread as fact. Three included Groudon, Kyogre and Umigorou by Datel, which were modified versions of Groudon, Kyogre, and Swampert to avoid legal trouble.
Four not listed on the above page are approximations of Palkia, Dialga, Chimchar and Piplup, which were used on the boxart of Action Replay DS. Other versions of the Action Replay DS such as Action Replay DSi and the 3DS re-release include others, such as (but not limited to) Mime Jr., Reshiram, Zekrom, Hippopotas, Ho-Oh.
An approximation of Dawn appears on a Japanese Action Replay codes book, with some unidentified monsters (may not be Pokémon).