Well, one element is similar - sounding words. Just like in the 'napkin' and 'diaper' story. Another is misinterpreting actions or intentions. For example, if someone waves at you to come closer but you think they are waving goodbye. And cultural differences can also lead to funny misunderstandings. For instance, in some cultures, nodding means no and shaking your head means yes, which can cause a lot of confusion.
Funny misunderstanding stories often involve miscommunication between people. This can be due to different accents. For example, a strong southern accent might make some words hard to understand for someone from the north. Also, body language can be misinterpreted. A person crossing their arms might be seen as defensive when they are just cold. And sometimes, our own pre - conceived notions can cause misunderstandings. If we expect someone to act a certain way and they don't, we might misunderstand their actions in a funny way.
First, language barriers play a big part. Different languages have words that might sound alike but mean completely different things. Second, lack of context. If you overhear a part of a conversation without the full context, you can easily misunderstand. For example, if you hear someone say 'I'm going to kill it' without knowing they are talking about acing a test. Third, assumptions also create funny misunderstandings. If you assume someone knows what you mean without being clear, it can lead to humorous situations.