Palette swaps
Nidoran♀ and Nidoran♂ evolution lines, regular and shiny.
A Clefairy duo recolored as a Haunter and a shiny Haunter. There used to be the full evo line, but the Cleffa and Clefable duos didn't look great due to Gastly and Gengar's very limited palettes.
/!\ TRANS RIGHTS /!\
Litten and Sprigatito swaps. Might end up doing the full evo line someday…