Funny or witty responses are more ideal for people you have a more casual relationship with. Friends, classmates would find these answers funny and would take it lightly. Furthermore, responding with a simple “I’m fine” can be overkill. Send a meme or something like “I was fine until you asked” or “It’s a secret.” These are great for lightening the mood and we all like to laugh on our misery. Don’t we?
Asking someone you meet “How are you?” is etiquette but they also expect a good response from the other person. You can respond to them in many ways but it depends on what kind of relationship you have with them. If they are a colleague or a stranger, reply with a smile and a positive tone. You can use phrases like “I’m great and how are you?” Ask them the same and maybe have a small talk if an interesting topic comes up.