Mild OCD runs in my family, and we all watch "Monk" and "As Good As It Gets" feeling very relieved we're not anywhere near that bad. My quirks were just that until the Graves' Disease hit. When my thyroid went out of whack it exaggerated many of them to nearly "Monk" levels, and not everything has gone back to my normal.
I can't run the dishwasher, washing machine or dryer without doing a critter count after the machine's door is closed for the last time. That often means heading up two flights of stairs to count critters and then back down to press "start." While in the grips of Graves' I found myself counting critters up to five times before starting a machine, and learned to understand how minor the problem was before.
I can't let DH leave for work in the morning without first having a three-way kiss session between him, me and the parrot (who sits on my shoulder, leans in and makes big "smacks." It's his favorite part of the day.), and then telling him to "Drive safely. Have a good day. We love you!" We greet DH each evening with another group kiss.
I grew up in an "ashtray in the sink" home, and Mom never backed out of the driveway without asking one of us to reassure her that we had also checked and the ashtray was in the sink. If nobody could confirm this, somebody had to run in and make sure. Over time, Mom has expanded this requirement so that now the ashtray must be in the sink with a little added water and another ashtray on top of it.