Several years ago I had a discussion with a friend about whether it was urban legend that a microwave could super heat water that would not burst into steam until the surface tension of the water was broken. My friend pointed out that Myth Busters had not been able to find any proof of this.
Well, I had it happen to me.
My wife and I have have been heating cocoa (AKA "coffee") cups of water in the microwave and then setting a baby bottle in the cup to warm up. We have repeated this process around 500 times in the last two months.
A couple of days ago I placed the baby bottle in the cup, and as the bottle touched the water surface, the water burst into a roaring boil for a few seconds. It was so strange that I didn't even realize what was happening until it was almost over. Luckily I only heated the water for 1 1/2 minutes, otherwise who knows.