I'd heard of Deja vu and didn't believe the sensation was possible until it happened to me the one and only time. I was watching a repeat of Digimon as a teenager and it happened when one of the Digimon characters on the show cries out 'JOOOE!!!' and it was like I could've sworn I'd seen that exact scene just recently or that I'd been in that moment before, because it seemed so familiar.

I'll never forget it because it's only happened that one time.

I think I'd be a bit freaked out if it happened regularly.