DS is autistic, aged 4.5. He's generally high-functioning but oh, when things are "wrong" it really upsets him.
For example, last night he screamed for hours simply because in his Elmer book there was a dressed-up tortoise on the last page which did not appear earlier in the book when all the other animals were deciding to dress up. He kept demanding that DH and I find the undecorated tortoise and wound himself up no end. We ended up drawing one and sticking one in 
Similarly there was a slight misprint or oversight in a Gruffalo activity book which meant that something couldn't be matched exactly because it was facing the wrong way. Thank Christ DH, DD and I can draw 
It isn't just these things. Today as we waked in from the town centre into the mall a pigeon was wandering around. He cried and cried. I'm sure it was because it messed with his idea of what is right.
He also can NOT, ever, stop something until he has seen it through till the bitter end. If he is re-telling a story or singing a song, for example. There is no distraction that works in any way. If a double-decker bus was hurtling towards him he would not interrupt whatever he was doing.
I know it's to do with restricted thinking and I feel very sad that DS' world can be so easily turned upside down by such little things. Is it that he is feeling a loss of control because his previous reliable perceptions have been shattered? I wish I knew more about it, and how to help him 