I am the youngest of 4 kids.
My brother and my sisters told me that “every 4th child born in the world is Chinese” and therefore, since I was the 4th, I was Chinese!
They would speak to me in “Chinese”, and I was very upset that I could not understand them.
This was just a misunderstanding on my part. When I was about 5, some distant relative died. I heard the grown-ups talking about the details. When the day came, and I realized I was to stay home with a babysitter, I was beside myself. I couldn’t understand why they all got to go see the polar bears and I couldn’t. I still secretly look for them whenever I pass a cemetery holding service. So far, I’ve missed them.
My son’s dad had him convinced that “pool sharks” lived in the pool filter.
I taught my 6 year-old niece that the correct way to burp is to cross your eyes and do it out the side of your mouth.
My brother and brother-in-law thought it was hilarious. Her mother and my mother were not very pleased.
Why polar bears?..ohh… I just got it. That’s funny.
Mine isn’t so funny. I convinced my very young cousin (I was 11, he was 4) That there was a monster in my closet with all my toys. He couldn’ tell anyone because it was a secret between us (not wanting to get in trouble for telling him there was a monster in my closet)and the monster would get him if he told. Eventually he started to mention that his cousin and he had a secret… and to his parents it sounded like a very BAD and disturbing secret. It was pretty tense apparently until he told them that it was a monster that guarded my GI JOES. It was clear to them then that I had mae up the monster so he wouldn’t try to play with my toys.
My dad told me that peanut butter was peanuts that were chewed up by dogs like ours at the time (a truly awful chihuahua-poodle-terrier mix who hated me) and spit into jars.
He also taught me this rhyme:
Good night, sleep tight,
Don’t let the bedbugs bite.
If they do,
Crack 'em in two
And eat them like the monkeys do.
You’ve never heard the second half of that rhyme you say? I was in college before I realized that no one had heard it.
I hadn’t heard that one either, but I am familiar with
Oh, say can you see
Any bedbugs on me?
If you do, pick a few
'Cause I got them from you.
I was reading a book the other day when the narrator (a large black alley cat named Midnight Louie) meets a bunch of Kiwi birds. He understands that he can’t eat them, but his roommate (a human female) has these things called kiwi fruit on her counter. He assumes that these round, brown fuzzy things must be kiwi EGGS and decides to eat one. He is horrified when green squishy stuff comes out. The roommate is not pleased either–and is rather puzzled as to why her cat wants to eat fruit.
The book in question is Cat in a Kiwi Con by Carole Nelson Douglas and is part of her Midnight Louie mystery series.
My grandpa told me they were fish eyes. I never believed him because I knew we were the only ones in the family who liked tapioca and he just wanted me to leave the rest of it to him. 
I’ll always remember that every time I see tapioca pudding.
When I was a kid I used to follow my aunt around the house incessantly. One day I knocked on the bathroom door and asked her what she was doing in there. She irritably told me that she was washing her hair in the toilet. Wow! Aunt Barbie washes her hair in the toilet! Cool! I was an adult before I realized she didn’t. Dangit! Another illusion ruined!
And I was the junior mom and did much of the raising of my younger brother & sister. One day I told my sister, when she asked how I knew she’d been playing with my makeup, that I had eyes in the back of my head. I didn’t realize she took that literally until we were talking about it when she was 16 or 17. She said that at night, she’d lift the hair on the back of my head while I was asleep, hoping to find my other set of eyes.
I convinced my friend’s kids once that the chocolate chip cookies I had just brought over had chopped-up toasted crickets instead of nuts.
And I also convinced that same friend’s kids that I couldn’t get up and chase them around the house because my butt was glued to the chair. After they spent an hour or so trying to pull me out of the chair, they believed me. I got some very indignant glances when I got up when it was time for me to leave.
Am I the only one picturing Eve holding a tiny plastic shovel, covered in dirt, and weeping with bitter disappointment?
“Where are the skull-hull-hull-hulllz?”
Back To The OP
I usually stick with “I told you how I did it- magic.”
I do tell my niece that she’s always safe sleeping in Bubby’s bed because Bubby’s snoring scares away monsters. This isn’t really a lie. Wolves and bears would be scared off by my mother’s snoring.
I’m pretty sure I posted these before. My ‘greates hits’ you could say 
I told my kids I was Santa Claus. They asked to see the reindeer. I told them I kept the reindeer in the shed all year long…but they’d better not try to get in to see them, because I didn’t feed them all year, so any kid who stumbled in would likely get eaten. Then I’d periodically ask “Who wants to go pet the reindeer??”
I told them there’s two ways to get chocolate - you can drill for the liquid kind (like hersheys’ syrup) but to get the solid stuff you had to mine.
We went to a company picnic where lobster was served. I told the kids lobsters are just big ocean-going bugs, and then got a couple. Probably not too many parents get to tell their kids to “Sit down and eat your bug!”
I told them I was 100 years old, my father is 1000.
One day when I was leaving for work, my daughter asked me where I was going? “To hunt aliens!” I cheerfully replied.
I also once told her I was going out to eat all the monsters. When I got back, a few hours later, she’d asked if I had. I said yes - I’d eaten every one of them. Some time after that (I want to say a couple of years) some one asked her if she was scared of monsters. “Nope,” she replied, “Daddy ate them all!” When the other kids came along & got to be old enough to be scared of monsters, she told them that I’d eaten them when she was a baby.
There’ve been a million of them, and I can only hope in the fullness of time when they have kids of their own, they’ll look back & grin evilly 
I remember a time when my nieces and nephews all wanted me to take my boots off, and I couldn’t understand why. Apparently on a previous occasion I had convinced them that I had “more toes than anyone else in the world,” and had forgotten that particular line of BS.
I’ll ask my kids tonight. I’m sure I spun loads of BS when they were younger.
That’s great.
When my younger boy was three he proudly proclaimed to his grandparents that he had been a “twinkle in Dad’s eye” before he was in his mom’s tummy.
Actually http://www.straightdope.com/classics/a2_304.html One guy wrote and said it messes them up if they’re open, so they might protect them somewhat.
I told my son that I can ‘read brains’; you know how sometimes, it’s so obvious what they’re thinking, or what they’re going to do next? I used a few of these easy moments to convince him that i could read his mind whenever I wanted.
I also convinced him he had a magic finger that would unlock my car when he pointed it (it was, of course, being unlocked by the keyless remote in my pocket); I eventually had to spill the beans on that one because it looked like he was going start charging across roads and busy car parks to get there before anyone else.
I was once taking a kid on a tour of our museum. It’s in a residential area, and to get to another of our buildings, you have to pass some houses. There was a dog in one of the yards, and the kid started teasing it.
“I like to mess with dogs sometimes when they’re tied up,” he confessed to me with a grin.
“Ah, man, you shouldn’t do that,” I said, shaking my head. “Dogs have prehensile thumbs, don’tcha know?”
“They have what?” he asked, sounding worried.
“Prehensile thumbs,” I said, wiggling mine in demonstration. “You can’t see it all the time, but if you make them mad enough, dogs can actually unclip their collars, and open gates. I’ve seen it happen.”
“No foolin’?” he asked, concern wrinkling his face. “They really can do that?”
“Sure can,” I said in my Museum Lady Voice of Authority. “If they get mad enough, they’ll get themselves loose and you might get bitten. I wouldn’t mess with them if I were you.”
Yeah, I lied, but maybe it will keep the little bastard from getting his ass bitten one day, and save some poor tormented dog from being put to sleep.
I usually helped a friend of mine each year with the annual sheep shearing, and this year I brought my son who was a little over three years old. I had told my son that the sheep had gotten to know my buddy and they had become friends with him. I told him to listen to the sheep as we walked up to the barn because they all knew my friend and would call out his name.
And, sure enough, they did. My son was astonished.
Brad was amused, too.
My mother told my very gullible sister that the little styrofoam balls sometimes found in planting mix were ant eggs–she went around dousing every houseplant with Raid to prevent them from hatching, and told several of her friends they had ant eggs and had better do something about them–she was in her late teens by then! Yeah, she was teased unmercifully…
My then ten year old daughter and I were observing a young female cat in the throes of heat and she asked me, in a VERY worried tone, “Mom… PEOPLE don’t go into heat, do they?” To which I cheerfully replied “Oh yeah, you didn’t know that? Every month honey, it’s part of growing up!” The look on her face was so priceless I couldn’t keep it up more than about ten minutes before I cracked up and confessed I was funning her… I THINK she’s forgiven me!
When I was very little, I’d want to show my grandfather “stuff,” like tots do. “Come look papa look what I found.”
When he was tired, he’d tell me he couldn’t walk anymore, because he had a bone in his knee. Then he’s bend said knee, and sure enough, I could see that knee cap. I was 7 when I finally discovered I too had bones in my knees and I walked perfectly well!
He used it on my much younger cousins when I was a teenager, but I didn’t give his secret away, they wore me out too!
He would let me “help” with projects around the house, and of course, I was mostly in the way. When I got to be too much of a distraction, he’d send me off to the garage, where there was a drawer with just about everything in it. Usually, I’d be in there looking for sky hooks and water dryers. I’m sure they’re still in that drawer, I just never figured out what they looked like.
This is my favorite!
My contribution: My children, 8 and 11, believe as surely as the sun comes up each morning that Mothers Don’t Fart. Never, ever. I was beginning to suspect recently that the 11 year old knew the jig was up when she told me she learned from a book that “EVERYBODY farts, Mom!” Nope, not me. Not mothers. And the other night, when I ripped a really rank one, she totally blamed the baby. Never crossed her mind that it might be me! Muhahaha.