LOL. I've learned my lesson in the past. I NEVER use market orders, precisely for this reason. $0.20 isn't too bad, I'm like the rest of the group I read that as $20.
Another thing I found out about option orders during the market open: Occasionally I go away on holiday for a few days where I'm incommunicado, so I place limit GTC orders to close out my options. Occasionally the underlying has gapped up and my limit price for selling my call option is now less than the option's intrinsic value. Without fail, the MM's will lower the bid for a few seconds at the open so that they fill me at my limit price.