What made Queen Elizabeth say, 'Boom, really -- please,' to President Obama and the first lady?

An Invictus Games rivalry played out on Twitter on Friday. The responsible parties? The Obamas and Prince Harry and his grandmother, the queen of England. The first strike came from Michelle Obama in a short video: "Hey, Prince Harry, remember when you told us to bring it at the Invictus Games?" Her husband then warned in jest, "Careful what you wish for."

The prince just happened to view the video message with Queen Elizabeth. Her response? "Boom, really -- please."

Boom. The competition at the Invictus Games promises to be just as stiff.

Tune into the Invictus Games May 8-12 on ESPN2 and ESPN3. Click here and scroll down for the TV schedule.