In a fanfiction with this theme, it could explore how their 'hard knock life' experiences shape their characters differently. Tony might use his wits to survive the cut - throat business world earlier, while Steve could be more focused on community and helping those around him. Their paths cross when they realize they are both fighting for a better world, but from different angles.
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.
One common theme is struggle. Just like in the 'hard knock life' concept, Avengers in these fanfictions often face extreme difficulties. For example, they might struggle with a lack of resources while fighting a new, powerful enemy. Another theme could be redemption. A character who has made mistakes in the past tries to make up for it during a tough situation. Also, friendship and teamwork are emphasized. In a hard knock life scenario, the Avengers have to rely on each other more than ever, showing the strength of their bonds.
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.