A rom hack of Pokemon Yellow based on the Pokemon Yellow Disassembly that replaces Pikachu with Hattrem! There are a few changes such as new NPCS (coming soon!), new rooms(also coming soon!), new moves/types, and a few quality of life features. The game is still mostly in a demo state considering the lack of other features, but you can finish the entire game with Hattrem if you want to.
To patch, you'll either need the Flips patcher for Windows, or an online rom patcher. You can only patch to a US rom of Pokemon Yellow.
You can find more of the pret community's disassemblies here!