(TMZ) -- Despite having a pretty rough week, Michelle Obama found some time to smile and goof around with LeBron and the rest of the Cavs on Thursday ... pulling off a Mannequin Challenge at the White House!
The Cavs were at 1600 Penn. to be honored by Obama for winning the NBA championship -- and decided to get in on the social media craze while there.
No sign of Barack ... guessing he wasn't in the mood.
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