My original impetus was to create a "First time I heard X" thread, since I find that I often have a strong and fond memory of the first time I heard certain songs that have stayed important to me over the years. But I don't want to limit it like that. That's the basic idea, though: maybe the first time you heard/saw a piece of music/art that has held a string of meaning for you throughout your life.
The first time I heard They Might Be Giants' "Why Does the Sun Shine?" I was in 7th or 8th grade. My friend Jenny had heard that TMBG had a phone number you could call to listen to a song. (This was early 90s, before the modern internet where you can hear any song at any time.) We asked her mom if it was OK since it was a long distance number and that mattered at the time, she said it was fine, so we called it. We sat in her dad's office where the phone was, sharing the handset between our ears, listening to this goofy song about the sun. I figured at the time that they just put some silly song up there that would never be heard again, but in fact it has become quite well-known and a standby of my parenting- we sing it on long road trips. My son can match the inflection in the spoken parts perfectly.
The first time I heard Stravinsky's Rite of Spring was on Saturday Night Live (episodes from the 70s that were rerun on Nick at Nite in the 80s). The Coneheads were escaping New York and part of it was the soundtrack to their escape. The part they used was near the beginning of this passage, the part with the flute trills:
My sister and I thought it was HILARIOUS at the time. What is this crazy music? Like, what the hell, seriously? It has become one of my favorite pieces of music, maybe my very most favoritest, and actually a minor obsession of mine (the music as well as the ballet and the story of its disastrous debut and later redemption), but still when I hear this passage I think of Dan Ackroyd drinking gasoline when the Coneheads stopped for gas as they escaped New York. (I couldn't find a clip of that, sadly.)
More to come, probably.
Edit: I added spoiler tags to the videos because for some reason embedded videos make pages load slowly.