Some thoughts on what I've "heard" about;
Family members who tell the same story over and over again,
Family members who railroad a discussion about one topic into a story that "you all can relate to," but they can't,
Kids who translate "Don't touch," into "Touch everything you can get your hands on,"
Kids who already know what they're going to get, because they have told, emailed and Facebook reminded the entire family over and over, so the "surprise," of opening presents now becomes checking off a checklist in their mind,
The unspoken, "Who farted?" game,
The doggie "presents" left on Christmas day,
The kitty regurgitated "presents" shown (in front of everyone) on Christmas day,
If you are single, and bring a significant other, the kids start to ask, "So, are you having sex? Mom says you must be. What's it like?"
I could go on, what have you experienced?