When i was a kid I was always rummaging in my dad's toy box (tool box), much to his annoyance. Then at some point around the age of 8 I worked out that all his steel bone shaped things were something to do with the little hexagonal things on my bike, and started loosening the seat post, wheel nuts and brake blocks and tightening them back up again. The biggest learning curve was when i found a spanner big enough to fit the headset on my Raleigh Tomahawk and undid that, only to watch all the tiny ball bearings scatter all over the garage floor. The challenge was to put it back together before Dad got home from work, otherwise i'd get a bollocking. I'm sure only 20% of the headset bearings went back in but it seemed to work afterwards.
When i was about 10, Dad got hold of an old frame from a workmate and some wheels from a skip and various other bits and we built a bike together, which first meant stripping the frame back to the metal and repainting it. I got Dad's big spanner and suggested we removed the forks. Dad suggested we didn't. I insisted it was fine, we just needed something to catch all the ball bearings in. I remember his perplexed expression to this day as I undid the forks and let the bearings drop into a big stork margarine tub, he was probably wondering how i knew what was going to happen.
I was a terrible as a kid for dismantling stuff then trying to put it back together before Dad found out... I think I almost always got away with it too.