My childhood was RULED by Star Wars. Some of my earliest memories are of Star Wars. I remember before Empire came out watching the first at my uncle's place, and being confused because I had remembered more wookies. This memory seemed highly suspect for many many years (VCRs weren't yet common, so how could I have watched it?) until I learned a) Star Wars was released on 8mm, though it was very rare. My uncle had it. I must have seen it in the theaters when I was too small to remember much, because my memories are of watching it again. And, of course b) my wookie memories were from the Star Wars Holiday Special. Which was aired once (November 1978). I was born August 1977, so I'm pretty sure that counts as my earliest memory.
And the moment that I realized these events had actually happened, and I was remembering things not making them up? My mind was blown.
Though if we're going for trauma, seeing Watership Down sort of backfired. I loved it, and don't remember being into horror before, but definitely after!