WARNING: THIS STORY IS GROSS!
There was this lady, and she loved mayonnaise. She loved it so much, she ate an entire jar of mayonnaise every day. One of her favorite things to do was lie in bed at night, and eat mayonnaise straight out of the jar, with a big spoon. When the jar was empty, she left it on the nightstand with the spoon in it.
One morning, after she’d eaten an entire jar of mayonnaise in bed, she woke up and the jar of mayonnaise on her nightstand was full. She was very surprised, but she figured maybe she had dreamed eating the entire jar of mayonnaise the night before. She took a big spoonful out of the full jar and ate it. Delicious!
By the time night rolled around, she had finished the entire jar. She set the empty mayonnaise jar on her nightstand, and she went to bed. The next morning, to her shock, the jar of mayonnaise was full again.
Like before, she ate the entire jar of mayonnaise throughout the course of the day. But now, she was determined to find out what was going on. It couldn’t have been a dream two nights in a row. So, she turned out the light, and settled under her blankets, and she pretended to sleep.
After a couple of hours, her bedroom filled with an eerie glow. As she watched, through her just-barely open eyelids, a ghostly arm emerged from the wall above her nightstand. It was a disembodied arm, cut off at the elbow and, as it hovered over the empty jar of mayonnaise, it turned in the air so that the cut-off end, with two knobs of bone protruding, was pointed down at the mouth of the jar. As the lady watched in frozen horror, glowing ghost pus poured from the severed arm, and filled the mayonnaise jar.
When the jar was full, the ghostly arm disappeared.
I’ve googled around for this particular urban legend, but I’ve never been able to locate a source, or any other mention of it. It’s somewhat similar to the infamous mayo chicken sandwich urban legend that emerged in the 1990s. (If you don’t know what I’m talking about, DO NOT GOOGLE THAT.) But, I was in elementary school in the 1970s. It seems like it might be something out of Scary Stories to Tell in the Dark, but it’s not in those books. There are some similar stories, but those all seem to be about somebody eating a dead person’s toe or liver, and then the dead person coming back to retrieve it. ¯\_(ツ)_/¯