I think this is something that will interest more people here.
Over the years I have played video games less and less. Last year I sold off my consoles and games. I have come to the mind set that if its collecting dust in a box under a box then it needs to go to someone that is going to appreciate it as nostalgia or as a first experience.
That said, I did keep a few cartridges even through I can't play them. Those were Mario Paint, Fanal Fantasy 3(6) and The Guardian Legend.
Recently went out to the same shop that I sold my stuff. We were there to pickup the sales were made off our posters and stickers. I decided that I wanted to get one of those Retrocons with some of my store credit. I told my friend about the strange glitch that I got in Final Fantasy3(6) and wondered if it was still on the cart all these years later.
Got home that evening and plugged in the console, popped in the game and there it was. An 80 hour play through that held the rewards of the glitch.
I will describe what happened as best I remember since that was 27 years ago.

Played through the game up to the point where you face off against Kefka, General Leo and the Emperor on the floating continent. (Want to say that I had been using an unofficial FF guide that was written off the japanese version of the game and used a few different or untranslated names. So, I was able to get the Chainsaw for Edgar, unlock Umaro, Gogo and Shadow)
The glitch that happened was in the World of Ruin while I was grinding levels for my lesser used characters. I would use one high level with three low to give them some defense while wondering around the world. This one was a group that had Umaro Relm, Locke and on other. We entered a random encounter and the screen went black for a whole second and when the combat screen came up the 4th person was missing Locke and Realm were there and Umaro was replaced with General Leo with vanished cast on him making it looked like it was his ghost fighting with us.
Its a shame that it was against some weak randoms but we fought and I got to use Leo's Shock ability and we won the day.
When the battle summery came up the background was black (I changed mine to a pattern color) and the summery was long listing a lot of weapons, armor, items and relics. Right after I went into my menu and Leo was not there but all the items were.
Some items maxed out at 99 and some had either a 0 or 1% next to them. This included Excaliber, Genji Glove, Snow Muffler and Economizer Eggs.
Now, technically there is only one Economizer Egg in the game but you can go to one forest and farm them for hours. This item reduces your magic cost for any spell to 1. Meaning that if you had Ultima it would cost 1 instead of 20.

As far as I can tell, this type of General Leo ghost has not been reported by anyone else on reddit or youtube. The General Leo that I have found required a lengthy set of steps to get Leo as a party member but not as a ghost and no item glitch as well.

I am glad that I still have the save and I know that it could be lost any time now if the save is dependent on the battery.
This is something that I don't get to share because no one is interested in something like this. I just wanted to get it down somewhere as a good memory and maybe there is someone out there that knows what this glitch is.