When I was growing up, my dad was a fantasy nut who got me reading The Hobbit and a bunch of stuff I don't really remember now (there was some David Eddings stuff in there, I'm sure, and the Bernard Cornwell Arthur books) but certainly inspired me to start writing fantasy stories when I was a kid. I also devoured the Tamora Pierce novels when I discovered them at school. Strong female heroines! Yay!
Movie wise, I was obsessed as a kid with these three: Labyrinth, The Dark Crystal, and Jan Svankmajer's Alice (a masterpiece of dark and creepy stop motion, incidentally!). I also had (and have!) an incredible fondness for Ray Harryhausen's animations. I adored the Sinbad movies, Jason & the Argonauts, Clash of the Titans, and others. I also really really loved Barbarella even if the sex references (uhm, yes, that's most of the movie...) went way over my head. It did spark my imagination for sci-fi/fantasy though

Oh! Krull! Have you guys seen Krull? It's terrible and amazing all at once. It's a glorious sci-fi/fantasy blend with one of my favourite character introductions ever (Ergo the Magnificent!). And Star Wars goes without saying. I don't remember when I saw it, but I absolutely remember wanting to be Princess Leia and shooting a blaster while my brothers were both being Luke Skywalkers fighting with my dad who would do the lightsaber noises and the breathing noises XD
Aaaand yeah, I nerded around with things like Master of Magic, Caesar 2 (and the later games like Pharaoh) in terms of computer games. I remember being addicted to Heroes of Might and Magic (we played hotseat multi, my brothers and I) and then the Might & Magic games where you had a first person party. Oh! Dungeon Master! I loved that! I remember mapping the dungeon out on grid-paper as I played and insisting on assembling an all-female party from the hall of portraits

edit: Forgot, we had a Snes and I adored Legend of Zelda: A Link to the Past and Secret of Mana. Also played a bunch of other games on there ofc, and got a N64 later for Zelda and Starfox. And Gameboy for Pokémon.
My first experience of D&D was via Baldur's Gate, which was recommended to me by my nerdy uncle because I'd adored Diablo so much
I never had a eureka moment, I was just a dorky child who enjoyed books and things because we moved around a lot so it was easier to just be boring than make friends and play outside with strangers every two years

At some point I must have figured out that it was kind of weird, because I remember I didn't ever go into much detail to people about what I was interested in.