Being woken up at 3 am because the child you're carrying first decides it's a PERFECT time to kick in every conceivable direction as hard as they can, followed by a two hour bout of hiccups.
When you are all into the Internets and writing stuff and then you suddenly and without warning have to pee so bad that you can't hardly stand up. Of course, it might just be the ten gallons of coffee I just slurped up like a fiend.
I was on this train once in Italy, and this guy was using his 3 year old daughter to beg for money. They where both dressed in expensive clothing, and his 'we have no food' like would have worked better if he wasn't 100lbs overweight.