Ok, ive read that NES games have 2 roms. One chip is for the game the other is for the sprites/tiles. If I were to leave the game ROM alone, but hack the tiles/sprites and burn that to a rom, and solder that in the cart, would that work?

 
Basically, if it works in your emulator, it'll work on the real cart.

Keep in mind the CHR is just the tiles, while the PRG is how those tiles are laid out, as well as the color palette being used.

So if you found the tiles that make up Mario's head, you could alter those and then your Mario would be running around with a different head.

Most games have a separate CHR and PRG chip.  Keep in mind some games (like an UNROM based game) use RAM for the CHR, meaning there is really just one programmed chip and the CHR tiles ar copied (or created) there from the PRG.


The hack called Super Mario Clouds did the opposite.  They left the CHR data alone and just modified the PRG code to display those sprites differently.

Al

Just a quick correction: if it works in a GOOD emulator, it is likely to work on the real NES. Good emulators include the most recent versions of Nintendulator, FCEU, Nestopia. Nesticle and anything based on it are absolutely not good emulators. The incorrect emulation in Nesticle is the reason many hacks and early homebrew games do not run on the real system.

Does anyone know of someone that will make hacks into carts for me if I supply the ROMs?

^ You might want to try the guys at nesreproductions.com and gamereproductions.com as a start.

I will try there, I was hoping not to pay $25 per hacked game

mario adventure is one that doesnt work on a real nes.  sucks too because it is pretty fun.