I found it at a garage sale in the summer. A Pokemon Red cartridge in a ziploc bag, no box, the label slightly water-damaged, sold for a quarter by an older woman who said it had belonged to her nephew.
I almost didn't check the save file first. Almost.
The trainer was named ??? — three question marks, the same display the game uses when it doesn't know what to show. He had six Pokemon in his party. All six showed the small icon that indicated they had fainted. But in Pokemon Red, fainted Pokemon recover at a Pokemon Center; they aren't listed as fainted on the party screen for any longer than it takes to walk to the nearest one. These six had been in the fainted state long enough that the game had apparently given up trying to display their HP bars normally. The numbers read 000/000.
I went to the PC to withdraw a different Pokemon and found the storage boxes full. Every slot in every box was occupied by a fainted Pokemon. Every single one registered 000/000 HP. Some of them had names I recognized — Bulbasaur, Pidgey, Rattata — but others had names that didn't correspond to any species I knew. The game displayed them with the question mark sprite the game uses for MissingNo variants.
I tried to start a new game.
The game would not let me. The new game option was present on the menu, and I could select it, and it would begin the intro sequence with Professor Oak's speech, but when it came to the moment where Oak says "Are you a boy or a girl?" the game paused, and then Oak said something different. The text rendered slowly, one character at a time:
"There is only one trainer. He is still trying."
Then the screen faded to black and loaded the ??? save file again.
I tried removing the battery — the internal save battery that keeps the game file alive — thinking that clearing the save data would reset it. I opened the cartridge with a tri-wing screwdriver. The battery was there, soldered in, standard CR2025. But when I touched it, the metal was warm. Not warm from the sun or from my hands. Warm in the way that living things are warm.
I replaced it anyway. Resoldered a new battery. Reinserted the cartridge.
The save file was still there. ??? still stood in Pallet Town surrounded by his dead Pokemon, the grass around him replaced with a deep red that the game's palette didn't normally contain. No building had a door. The path north to Route 1 ended at a wall of solid black.
He could walk around the town. He couldn't leave. He couldn't reach a Pokemon Center. He couldn't do anything except move through the red-tinted version of Pallet Town indefinitely, surrounded by Pokemon that had stopped registering as alive.
The game has a mechanic for this. If all of your Pokemon faint, you black out and return to the last Pokemon Center you visited. ??? never blacked out. The game didn't seem to recognize that his situation met the conditions for blacking out. He just kept walking.
I left the cartridge on. Went to bed. Came back in the morning.
??? was still walking. The battery on my Game Boy was somehow not depleted. He had covered the same ground in Pallet Town thousands of times through the night.
He was still trying.
I don't have the cartridge anymore. I left it at a different garage sale, in a ziploc bag, priced at a quarter.
I hope whoever bought it checks the save file first.