One thing you have to know before you read what's below is that my dad sometimes buys stuff he doesn't even know about, but it's for a cheap price so he gets it.
When I was about 6, my older brother (14 at the time) would borrow me his iPod sometimes. And so I was listening and listening and listening and there was a whole load of awesome bands I like today (Sum 41, NOFX, Blink-182, Good Charlotte, Green Day). But Green Day was just a part of it, they never stood out to me. About 3 years later we went to the store to get something my dad wanted and then he said we can get Green Day's International Superhits album because they sold it for a cheap price (5 Euro). Then I thought "Oh, Green Day is that cool band my brother had on his iPod!". So we bought it. I opened it and played it in the car right away. Wooooah that album blew me away! I don't know, after 3 years of not listening to Green Day I just played International Superhits and woah, Maria came on and man was it awesome!
So I looked them up on YouTube and I quickly got Warning and Nimrod. The next year Breakdown was released and I got it, then I got American Idiot, and blkdjfgzoldfuinzpdirugn That is when Green Day became my favorite band.