Music Meister Explains Himself - The Flash Season 3 Episode 17
The villain of the story...wasn't a villain at all. Music Meister wanted to teach Barry and Kara a lesson about love. That's why Iris and Mon-El were able to save them. A bit of a risky move, but a nice twist on the musical ending.
Cisco [to Wally]: We win and we lose as a team. I'm coming with you. J'onn: Me too. Cisco: Look, J'onn. I respect this whole special agent situation you've got going on. But this problem right here needs someone with... J'onn: [transforms to his Martian form] Cisco: ...green skin and a sick ass cape. J'onn: Call me the Martian Manhunter. Mon-El: I think you'll find that J'onn's a lot more than just a pretty face.
Barry [singing]: I'm your super friend. Your super friend. I'll be there in the nick of time if you're ever in a spot. Kara [singing]: And if not there in time, you can just go back in time and give it another shot! Barry: I'm actually not supposed to do that anymore.