The shush is part of a public-service announcement for Obama's national fitness campaign, Let's Move.
In the one-minute spot, Obama and tennis power couple Andre Agassi and Steffi Graf play ball girls (and boy) watching a tennis match between 9-year-old Alexa Orlando and another girl. During a break in the action, the first lady encourages kids to play an hour a day, prompting Alexa to turn and shush her before her next serve.
Obama appears to silently mouth the word, "Sorry."
Alexa's mother said Wednesday that the first lady's involvement was kept secret from the participating families until the night before the video was shot last month.
Mona Orlando said The Tennis Center in College Park invited students to audition through the U.S. Tennis Association. She said her daughter had never done anything like that before, but wanted to try.
“One thing led to the next,” Mona Orlando told Frederick County Public Schools, “and she was selected.”
Vox Populi said the PSA was filmed last month at Yates Field House at Georgetown University.