I was short 15 AMD puts at 27.5 Friday afternoon. AMD closed at 27.85. I marked the puts Expired in my spreadsheet. I was surprised Saturday morning to receive notification that 14 of the contracts had been assigned. I checked the after hours trading and it was flat line. Why would anyone sell me stock for 27.50 when they could sell it in the market for 27.85? I have traded thousands of option contracts and never been assigned an OTM option. I typically carry deep in the money puts and have never been assigned early so long as the put still has some time value. Bizarre. Perhaps the best explanation is that someone made a mistake.