A couple of weeks ago DS was asking about the smoke alarms so, without thinking, I pressed the 'test' button on the one in our hall to demonstrate the noise they made. DS refused to go into the hall or go down the stairs by himself for a week and still shoots it nervous looks, asking, "It won't make a loud noise, mummy?" every time 
Yesterday 2yo DS was prescribed a brown inhaler to go with the blue one he's been having for a year. He screamed the house down yesterday evening when we tried to give it to him, thrashing and sobbing, so I cunningly swapped the cannister in his blue one for the brown one and tricked him into taking it. He was unimpressed and made the same fuss when I swapped the canisters back and tried to give him the blue one, so to prove that it wasn't the smelly horrible brown one I puffed it in his face for him to sniff I don't know what I was thinking but he looked at me in utter shock and outrage and waahed loudly into DH's shoulder. Oh dear.
Care to share any other non-serious parenting fail moments to make me feel better?