Leave it to Mick Jagger to get a staid White House crowd out of its seat during a celebration of the blues Monday night in the East Room. Just after 8 p.m., the White House Twitter account jokingly boasted, “Wait, did Mick Jagger just take the stage?” Indeed he did, and he jacked up Obama and Michelle, who clapped and swayed — not too awkwardly, either. The concert’s star-studded lineup for the “Red White and Blues” also included 86-year-old blues legend B.B. King, plus Jeff Beck. Jagger said he’d been a blues admirer since he was a kid.