I'm going to have to think about that - I'm sure we have quirks, but they seem normal to us! Your first one did make me think of one of ours - we do say Happy Birthday to each other, but it's also likely to be anything but. Instead, we say Happy Easter, Happy Father's Day, etc.
My husband and I keep the same seats at the dinner table but the kids rotate, seaonally. They think it's so that they get a change; we know it's so that we get a break from looking at each particular child's eating habits!
Small wrapped presents are always guessed as undies - obligatory.
