Let's say I sell a call option and before expiration date, it is out of the money. The buyer would not exercise it normally. I am just curious as to what would happen to my account if he does decide to exercise it irrationally?
If you sell a $100 call and the stock is $90, and somehow the broker lets the buyer exercise, you are short, at $100, and simply buy the stock for $90 to cover the short.
Your account value would increase by the amount the call was out-of-the-money plus the remaining call premium if any -- a fantastic windfall thanks to the irrational exerciser.
It would also be a good day for you to buy a lottery ticket. :)