Just in case you haven't already seen it, I highly recommend this week's episode of The Flash, "Duets". It's a crossover with Supergirl, and it's a musical! No, no, don't turn away yet! Grant Gustin (who plays Barry/The Flash) and Melissa Benoist (who plays Kara/Supergirl) both got their start on Glee, so they have musical chops. Several other actors from both shows, and Arrow, also have musical backgrounds, and they make the best use of them. (My fellow Doctor Who fans will especially appreciate John Barrowman doing his thing.) So why am I writing about it here? Because it turns out Supergirl's favorite musical is The Wizard of Oz, and she makes about a half-dozen references to it. So watch, enjoy!