Pharrell Williams Just Threatened To Sue Trump

Pharrell wasn't happy (no pun intended) that Donald Trump used his song "Happy" during a rally following the Pittsburgh Synagogue shooting.

So, he sent him a little cease and desist note as a heads up to stop using the song before he gets slapped with a lawsuit.

Actually, now that I think about it -- has anyone ever sued a President before? At least, while he's still in office?