I suspect many of us had siblings who told the occasional whopper, growing up.
My brother claimed they stopped making Bubble Yum since it was consistently contaminated with baby spiders.
I could go on… but maybe yours are more interesting.
I don’t remember doing any of that stuff to you.
Not my stories, but my mother, who had an older sister, Cheryl.
Cheryl told my mother that there really were eight days in a week, like in the Beatles song.
Cheryl told my mother that canned ham can be cooked inside the can.
I’ll ask her for other examples later.
Putting your finger in the light socket just tickles, its fun!
Never mind
Cheryl told my mother that Mount Rushmore in its current configuration was formed that way naturally.
Cheryl once told my mother that a tub of sour cream was ice cream.
Cheryl tickled my mother so much that she’s not ticklish anymore.
Cheryl beat my mother in chess (and rubbed it in her face) so much that my mother refuses to play chess against me.
My brother told me the distant HS marching band we could hear wasn’t marching bands, but “Martians Landing”. Of course they were going to take over the world.
StG
When we were little, my sister and my cousins teased us and told us we “slumbered” in our sleep! This made us deny it vehemently, and eventually we cried. We ran to Mom who undoubtedly hid her snickers while she told us what it meant, and fussed at the older kids to stop teasing us.
It’s actually pretty funny. 
My brother told me Father Christmas had died, so we weren’t getting any Christmas presents.
My husband’s sisters convinced the youngest at the age of about 6 or 7 that she was adopted because she had brown eyes while the others had blue. When she protested “but Mom has brown eyes!” they told her it didn’t matter, everyone else had blue so that meant she wasn’t really their sister.
Being too young to work out Mendelian genetics she was very upset at this news and believed it for some time.
I don’t personally remember it, but my big brother, trying to keep me from following him to the basement, told me, “There’s ghosts down there.” Later, Mom told me to go get her something from the basement, and I refused. “Ted says there are goats down there!”
Once my brother was wearing headphones, and I turned up the volume on him, then right back down again. He spent the next half hour pretending that he couldn’t hear anymore, or at least he pretended until I was crying, I’m not sure how long that took.
Oh, yeah, my siblings told me that Mother & Dad found me in the gutter and took pity on me and brought me home, because my eyes were green and they all had blue eyes.
StG
One year my brothers and I all told our mother that Chanukah started a week earlier than it really did. She never checked the calendar, so we started the eight nights, with presents and all, a week before the holiday actually began that year.
Then we tried to get a second eight nights by telling her at the end that we had just made a mistake. That didn’t work.
One year, shortly after Halloween, my younger brother and I were in the school library during “quiet study time.” He came up to me with a little box of Milk Duds and said “here, want these? I got too many of them.” I examined the box closely, suspecting trickery, but it was closed and seemed sealed. We weren’t allowed to have candy in the library, so I bent under the table, opened the box, and quickly poured the contents into my mouth. As I should have guessed, he had filled the box with small clods of dirt (very carefully–Milk Dud-sized clods) and re-sealed it. So I was stuck in the library with a mouth full of dirt. I turned red, coughed and retched, yelled at him, he fell on the floor laughing (literally. He enjoyed his jokes more than anyone) and we both ended up sent out into the hallway until we could learn to behave ourselves.