Do you think it would be funny if i sent a facebook friend request to my teacher?

[【ⅇMⅈLℽ】]

In general, I find it highly inappropriate. It wouldn't be funny - it'd be very intrusive. In my opinion, your relationship with your teacher should be nothing be than your relationship with your doctor, or your dentist. A professional that is meant to help you, but not on a personal level. Your academic life should be kept completely separate from your personal life - this is not a joke.

Unless the teacher is a close family friend or relative, then don't even think about it. For your own safety as well - countless times teachers have been arrested on sexual harassment charges. You'll never see these teachers again once you graduate - might as well keep them at an academic distance and leave it at that.