I didn't like how The Doctor was acting jealous and friend-zoned by Clara and Danny's relationship. It reminded me of how he treated Mickey Smith way back in 2005 and I think this version of The Doctor should be more mature than that by now.

I rewatched this episode only 2 weeks ago and yet I already can't remember the how or why of this monster of the week. Obviously the monster was just the excuse for The Doctor to bother Clara at her work, which is fine.