Years after I used to regular play Pokémon on the GBA with my brother, I picked it up again. I decided to start a new game and play through it all again. Just as I saved for the first time, I remembered my brother left me his near complete collection of level 100 legendaries to look after when he started a new game and we'd never transferred them back. I panicked, but thought it'd be fine/he'd have forgotten/it's been years, he's not gonna want them back now. Literally one week later he asked 'hey, do you still have all my legendary Pokémon?' It was a mistake but I still feel super guilty.