Basically, when I napped, he would wake up, the minute I thought "aaaah, he's asleep, I'll take a nap". After a while the only way I could sleep was if I held my mind completely blank and didn't think about him sleeping, I then could nap. Then, when he was a toddler, I would start to say something, and he would blurt out whatever word I was going to say. He only did it with me (but all the time, in front of other people). I'd open my mouth and he would anticipate the word I was going to say. He also did this once with my then minister, who I had a deep emotional bond with at the time.
There are other instances of this type of thing but these were the most common- and unusual, since he was not very verbal.