Earlier this year, we had dear friends stay with us for a few days who are missionaries. We worked with them in India in the mid 90's. The husband is a MK himself and he and I went to the same boarding school in India (although 15 years apart).
We were chatting about the funny things that you carry through your life as a result of the boarding school experience. My 'thing' is that I love, love, love, long hot (very hot) showers. This was because the boarding house that I lived in, had a water shortage. So we'd often have to have bucket baths at the main school during the lunch hour. These were 2 minute baths, with half a bucket of hot water and I had long hair. It was stressful. So it's not rocket science to work out why I love hot showers so much.
Our friend kept helping himself to copious amounts of milk out of the fridge while he stayed with us. Apparently this is his 'thing' that he's carried with him out of going to boarding school. When he was at school, his parents had to pay an extra fee for him to have extra milk for his afternoon tea - and his missionary parents couldn't afford to pay the extra. So he's spent a lifetime compensating!
I'm interested to know if other MK's have things like this. I suspect that I also find watching TV enjoyable because we never had TV when I was a little girl. My tales of my 'deprivations' do drive my family a bit mad though (lots of eye-rolling!).