Couple of lies I've told kids.
First one was a few years ago, I was working in a bar and it was Xmas Eve - all the girls had to dress in Mrs Santa outfits (inc. fishnet stockings). I slipped and fell and had four pint glasses in my hands - I sliced the top of my finger off.
Went to casualty and there was a 4 year old boy in there who'd fallen down the stairs looking for Santa (I was the only female, the rest were just drunken yobs).
Little boy yells to his mum - "Mummy, it's Mrs. Claus" and asks what I was doing in hospital. I told him that I had been feeding Rudolph a carrot and that he'd bitten me - he was so into my story that I ended up regaling him with tales of elves and Santa's workshop and stuff. Eventually he said "Mrs Claus, is Santa bringing me a bike?" - I looked over at his mum who nodded so I asked him if he'd been a good boy and he said he'd tried, so I told him if he went home to sleep after he got his stitches, he may just have a bike waiting for him.
Needless to say his mum loved me for taking kids mind off injury. I went back to the bar I worked and got drunk all night :) Yay.

2nd lie was to my (then) 4 year old cousin - Xmas Eve 2000. He was being a little shit, so I told him that the tracks in the sky (aeroplane tracks) were Santa's sleigh, so if he didn't behave he'd get nothing for Xmas.
( Batshitmentalist is sane for once, Fri 16 Jan 2004, 4:30, Reply)