This is an Eastern European (don't quote me on that, though) fairy tale my dad told me all the time when I was very, very young.
The Story of Bootalenik
There was once a little boy named Bootalenik, who lived deep in the woods with his mother. One day his mother had found work that would take her away from home most of the day. Everyday before she left, she'd tell Bootalenik
"When I'm gone don't let anyone in the house for any reason."
During these long hours home by himself, Bootalenik got very lonely, and often wished for someone to play with. Then one day he heard a scratching at his door. He opened it a crack and saw a fox sitting outside his door.
"Hello, little boy, what's your name?" the fox asked.
"Bootalenik."
"Nice to meet you Bootalenik, I'm Mishka. Can I come in?"
"My mother said I shouldn't let anyone into the house when she isn't here."
"If you let me in, I'll give you a ride on my bushy tail."
Bootalenik, lonely and wanting a playmate, let her in, and she gave him a ride on her busy tail. He had very much fun, and Mishka left right before his mother arrived home. Mishka returned day after day, and gave Bootalenik rides on her bushy tail. One day Bootalenik's mother had set his dinner out early for him, and when he let Mishka in, she ate all his dinner without giving him a ride on her bushy tail. When she returned the next day, Bootalenik wouldn't let Mishka back in.
"Why won't you let me come back in?" Mishka asked.
"Last time I let you in you ate all my dinner without giving me a ride on your bushy tail," said Bootalenik.
"But Bootalenik, I promise if you let me in this time I'll give you an extra long ride on my bushy tail, and won't eat your dinner. I promise."
Bootalenik, remembering how much fun it was to ride on Mishka's tail, opened the door and let her in. He got on her tail and out of the door she shot, into the woods and back to her den, kidnapping Bootalenik. When Bootalenik's mother came back home to find him not there, she cried and cried and cried. A woodsman heard her and went to see what was the matter. She told him her son was gone, and she didn't know where he was. The woodsman set out into the woods to find little Bootalenik. After many, many hours of searching, he heard a little boy yelling for help, and followed the sound. He found Mishka's den, and chased the fox out and away further into the woods, never to be seen again, before returning Bootalenik to his mother.
And from that day forward, Bootalenik listened to his mother and never let a stranger into the house again.