Once upon a time, there was a knock on the old, creaky door. Knock knock. A girl inside the haunted house froze in fear. Then she heard a scratching sound, scratch scratch, on the window. She slowly turned and saw a shadowy figure outside. It was the spirit of a long - dead miner who had died in a tragic accident in that very house. His eyes glowed red as he stared at her, and she knew she was in for a terrifying night.
Sure. Knock knock. A traveler was at an old inn. Scratch scratch. He heard strange noises outside his room. He opened the door, but no one was there. As he went back to bed, he felt something crawl under his covers. It was a small, bony hand. He realized the inn was built on an old graveyard, and the spirits were not happy about his presence.
The unexpectedness makes it scary. Just like in a 'knock knock' horror story, you don't know who or what is on the other side of the door. It could be a demon, a ghost, or some otherworldly entity. The simple act of knocking is something we associate with normal, friendly visits in real life. But in these stories, it becomes a harbinger of doom.
There was a young girl alone at home. Knock knock knock. She went to the door but no one was there. Again, knock knock knock. She peeked through the window and saw a shadowy figure. This time when the knock came, the door slowly creaked open. She screamed as a pair of cold hands reached for her.
Hard to say. Sometimes stories like 'Knock Knock' blend elements of truth and imagination. Maybe it has some roots in reality, but could also be largely made up for entertainment.
A 'knock knock' full story can be a long sequence of 'knock knock' jokes strung together. Let's say we start with 'knock knock', 'who's there?', 'Lettuce', 'Lettuce who?', 'Lettuce in, it's cold out here!'. Then we can follow with another one like 'knock knock', 'who's there?', 'Canoe', 'Canoe who?', 'Canoe help me with my homework?'. These jokes are simple yet can bring a smile or a laugh, and when told in a row, they make for an entertaining 'full story' of sorts.
In fact, 'Knock Knock' is purely imaginative. It was written and developed from the creative minds of the writers and not inspired by any true incidents.
You can start by using 'knock knock' as a buildup to a surprise or a mystery. Maybe have a character hear the knocks and wonder who or what's behind the door.