I'm new to this forum and I want to share with you my experience with a glitch I encountered in pokemon silver when I was a kid, since it has been a very long time that I was asking my self what happened exactly.
First of all, please excuse my English, this is not my mother language, so I'm probably going to do some grammatical mistakes, but I hope that my message will be understandable.
As I said all happened when I was a kid, even if I already exploited some of them, like cloning in G/S or obtaining mew in R/B at that time I didn't have real knowledge of how a glitch work and the one I'm going to explain you didn't make any sense to me. Before beginning, it is important to point out that it happened on a French version of pokemon silver.
The fact is simple to describe, I were playing the game quite normally and suddently two weird things happened to my surprise. I don't remember what happened first, but one thing is that the mom called to tell me she bought some new item for me and all excited, the first thing I did is to go checking the PC in my room to see if I have some new decorations and I got every single decoration that is possible to obtain in the game at once and I've never done a mystery gift for a reason I will explain later.
The second thing that happened has to do with the Trainer House, as when I tried to fight the trainer, instead of having the standard trainer with all the three starters' third evolution at level 50 I had a trainer with a glitchy name and some pokemon that was over level 100.
As far as I recall the name was samething similar to àé çb (that may not be the exact name) and some of the pokemon were, onix, donphan and houndoom (there were others but I can't remember). I could fight against this trainer without having the game freezing although the pokemons over level 100 were a bit difficult to beat I could manage to win, but the money I gained was just around 100.
I did some research myself to try to explain what happened, and I learned that in the trainer house the trainer you are going to fight is influenced by the mystery gift and there are some glitch linked to that, but from what I found on the internet, like the "trainer house glitches https://bulbapedia.bulbagarden.net/wiki/Trainer_House_glitches";, but it doesn't explain how I got all the mystery gift decoration at once.
About the mystery gift, I've said I've never did one, or at least, I never succeeded to do one. This is because I mistakenly bought a French version of pokemon silver, instead of the Italian version (which is my mother language, for instance this happened because in Switzerland we have four official languages and the store were I went sold pokemon in different languages and they mixed up everything -_- well I can't complain much since I could have mistakenly bought a German version that would have made the game nearly impossible to understand for me xD). For this reason I were the only kid with a French version and everybody else had an Italian version. I honestly never had problems to exchange pokemon or battle my friends in this situation, if we exclude the fact that the pokemon had different names in French. However the mystery gift never worked, I've tried multiple times, but there just were no way to make it work.
So in my conclusion, is it possible that doing a mystery gift between games in different languages could have activated those glitches?
However, I just think is strange that it happened only to me, but not with the people I've tried to do the mystery gift with.