I'm kind of surprised that others were surprised by Maisie Richardson-Sellers returning as Charlie on the show. I thought this was spoiled months ago--by Maisie herself--but I guess some managed to avoid the spoilers. I have to admire that, since I prefer not to be spoiled myself. I was happy that I didn't watch the promo for this episode as it was a thrill to see all the twists and turns it took.
I knew that Charlie had to be Maisie, but the episode still surprised me with how it all worked out. The episode title itself was oh so clever with its multiple implications, "Dancing Queen." Maybe LEGENDS' big problem is it's too clever for its own good--there are so many references that you could easily miss half of them. But I instantly knew what was going to happen with that Little Shop of Horrors plant--props for leaving some things to the imagination (in Nate's words).
I wonder what's going on with that Mona character. She can't be there by accident.
I think the real Sir Prize scene of the episode was John and Zari in that Liverpool pub and the paradox. Maybe it didn't advance any plots (but we did get a glimpse of the person threatening Constantine); however, it did display the many dimensions of this time travel show.