Last Friday night, Florence Welch surprised a random British cover band and made them play backup while she did karaoke to “Get Lucky.†She forgot most of the words, and her dancing is a little … free-form, which has led some commenters to speculate that Florence maybe had a few gin and slims before hopping up onstage. But before you judge, ask yourself two questions: Do you know all the words to “Get Lucky� And are you a graceful disco dancer? Right.