Friday we witnessed one of those obvious share price manipulations on Groupon's stock (GRPN). This is not a rogue trader gone wild. Nor is this a fat finger incident of entering the wrong lot size. Nor a glitch or news driven spike. No, friday was option expiration day. Right before expiration time, the value of options can be quite sensitive to last-minute extreme price changes in the underlying. In this case, literally 2 minutes before expiration, someone purchased 770k of GRPN stock and the price spiked from $22.50 to $25.15. An increase of 11% that required some serious fire power of approximately $18 million. During that time call options with strike prices of 24 and 25 had essentially gone in-the-money. It would be interesting to find out who would do something so obvious and blatantly criminal right before the close on option expiration day, since there is no other explanation than it being sheer manipulation. Take a look at the chart below to see what happened.