My suggestion, since you mentioned classic Pokemon and RPG Maker, is Pokemon Infinite Fusion, a fan made Pokemon game.
It is mostly a remake of the plot of the first games (Red/Blue/Yellow) but with a twist that you can now fuse any two Pokemon into one. For example, you could fuse your Bulbasaur and a Pidgey to make a new single Pokemon called Bulbagey, a flying grass type that has all the moves of both Pokemon, and can even evolve!
It is available for free and runs on PC, or with some effort it can run on Mac or Android.
My suggestion, since you mentioned classic Pokemon and RPG Maker, is Pokemon Infinite Fusion, a fan made Pokemon game.
It is mostly a remake of the plot of the first games (Red/Blue/Yellow) but with a twist that you can now fuse any two Pokemon into one. For example, you could fuse your Bulbasaur and a Pidgey to make a new single Pokemon called Bulbagey, a flying grass type that has all the moves of both Pokemon, and can even evolve!
It is available for free and runs on PC, or with some effort it can run on Mac or Android.