My biggest fail was when i just loaded up minecraft, first time ever playing not knowing anything, i was just digging) sand and dirt and punching wood, (not crafting anything since i didn't know how to). When night came i just kept dyeing and exploding, i thought creepers where cowboys masked in dark green (it was night and dark) with guns firing explosive things at me, and i thought skeletons where armored knights.
That was about 1-2 years ago....