I just bought a used copy of image fight  for NES from my local used game store. I turn it on and it is actually the game breakthru.

The label doesnt look changed, I also dont understand why if anyone would swap game boards inside the cart since these games are not rare or worth anything.

Any chance of this being a known error or a rarity? Anyone else ever experience this with any other game?  One game is made by data east the other by Irem.

Most likely a chip swap? Kind of annoying as I wanted to send this game to be reproduced into something else (Ironic, I know). but if its worth something then It wont be so dissapointing lol

perhaps they got mixed up when they where cleaned

Hmm that sounds like the most logical explanation.