EDIT: Thank you to all the kind words everyone, I will make sure my son see's the uplifting comments from this community. He is very proud of this, And I am not kidding that short of front panel connectors and the thermal compound it was boot ready when I saw it.
So this build was an honest accident, and is by no means permanent, as I have had plans to build 3 SFF PC's for my young children, but time has gotten in the way. But to start this off, one night my son and I were downstairs, and I was building a customer PC while he was gaming on Fenrir so we could spend some "Daddy and Me Time" as he calls it.
I have a large corner of scraps and teardowns as well as a bunch of legacy hardware and Graphics cards I pick up cheap or free from upgrades just... lying around lol. Out of nowhere, my son shuts down Minecraft (NEVER happens) and starts picking through the corner of boxes and setting certain things aside. I smiled to myself and continued on my merry way cable managing and boot testing the customer machine.
After about 20 minutes, my son asks Daddy what he uses to put together computers. I showed him my screwdriver/multi tool, cable cutters, zip ties, thermal grease, etc. You know, the works since they were all right next to me anyways. He seemed very interested, so I said to him he could build one tomorrow with Dad.
Well, lo and behold he built it while I was at work. Seriously... no manuals... no Youtube guide... Just the many computers he watched Dad build. Heck, Mom didn't even know he was there because the playroom is right next door and she thought he was in there playing lego. I came home, and because it was all tear down hardware I didn't even know if it would boot. He showed me it in pride and I couldn't help but grin. I asked if I could check it over, and short of cables everywhere and a bit liberal application of thermal paste (not bad actually, just a little heavy) it was all cabled right, and after the thermal reapplication it actually booted! I was stunned.
Long story short, I managed the cables, helped him install a few of those cards (Xonar, GTX 550 ti, USB Add In) that looked "Cool", and voila! a 6 year old built his own PC which is more than enough for his Minecraft. Enjoy all, wish I had more photos, but I didn't build it! ;)