I don't know which is my MOST careless one. So of them caused by ignorance or even stupidity. May be you folks can choose one for me:
1) I once built the Revell 1/32 Spritfire Mk I. I glued the left flap to the right wing and right flap to the left wing.
2) Similar to Case 1, I once glued the left propeller to the right engine in my Airfix P-38 and vice versa.
3) Trying to make my old Airfix 1/72 TBF Avenger looked remarkable, I once painted 12 tiny Japanese flags on it as kill marks.
4) After seeing the USAF insigna in the 70's, I thought the decal in my Monogram 1/48 P-47 Thunderbolt was wrong. So I add a red stripe on the white area on the insigna and painted the word 'USAF' on the wing.
5) While painting a F-4 Phantom with brush, the phone rang. I rushed to the phone but left the brush on the wing!! When I returned, the paint dried. I pulled the brush hard, leaving hair on the brush got sticken on the wing.
Well, when you were 14 years old, you did a lot of crazy things.