I have a friend with a clear retainer it is, I think. You can still see it though, and I hate how people are always making a show of taking them out. Ewww! The human mouth is so filthy and disgusting.
Ways to annoy people:
Arrive at a meeting late, say you're sorry, but you didn't have time for lunch, and you're going to be nibbling during the meeting. Then eat raw potatoes.
Ask people what gender they are,or
Disagree strongly with everything anybody says:)