When a famous person who generally stays out of politics suddenly becomes extremely political for seemingly no reason.
Harry Belafonte Syndrome was named for the actor and musician of the same name (Duh). He was very popular and famous until the mid-late 2000s, when he suddenly revealed that he is a registered democrat. Suddenly, he became an extreme liberal activist. He even said in 2012 that anyone who opposes the re-election of Barack Obama should be sent to prison. This statement landed him in very hot water, and he was harshly censured before effectively falling off the face of the earth. However, he is still alive, and his liberal activism is still dominant over his musical talent.