Do you think it would be funny to say goodnight when I'm not even going to sleep?
What is the point in your doing this?
I'm having fun because people will be sad about my goodbye.
Its wrong to lie to people about you having to leave. While it may be interesting to see how they would react, you are ultimately just going to make it difficult for them to trust you down the line.
It's not my fault if they believe that I'm leaving and that they care too much.
I think it would be your fault, though, because you're lying to them. I don't think this would be a very funny thing to do, and would only make you seem like you don't care about telling the truth.