I thought the black spots weren't part of Luna's cutie mark. Last time, when it was taken away, only the moon vanished. I assumed it's just her natural coat (and that it's naturally symmetrical). Hm, maybe that was just draining the power from the cutie mark.
Interesting dreams ponies have. Pinkie surfing on the gummyboard, wearing shades, I like that a lot, heh. And Derpy as queen, on her side another ... background character. ;-)
Starlight's dragon toothbrush was funny.
Twilight her frequent freakout self, but totally understandable why she couldn't calm herself. Still so much admiration for the regal sisters and projection of crucial importance to Equestria. (She underestimates the importance of everypony else's contribution.)
The episode was full with playfulness, action and lovely little details and a new insight into ponies' daily life.
I will close with one of my favorite pictures from olden times that immediately came to mind when realizing the theme of this episode. I call it "Maneheart"...