Had Matt Smith stayed on one more season, he would have had some proper adventures with Handles on Trenzalore.
Maybe some day we'll get Tales of Trenzalore on Big Finish.
btw, I found really good analysis of Listen from someone else on another forum.
I initially didn't like this episode at all. I found it pretentious and nonsensical. But then I listened to others ideas and watched it again and I think this is it.
The Doctor has been scared ever since he was a little boy (as Clara grabbed his ankles) and it's become such a default thing with him that he's actually scared of nothing. At the beginning of the episode, The Doctor feels scared - after all, besides the ankles thing, he has reason to be what with all he has encountered down the years - and he tries to rationalize it. He WANTS there to be something which has discovered 'perfect hiding' because then he has a reason to be scared. That way, he isn't scared of nothing, which is even more terrifying. The thing under the bedsheet was a manifestation of his subconscious. He's a Time Lord, after all, and he can summon that sort of thing while you or I or Clara wouldn't be able to. He needed something to be there - something to prove himself right, that there IS something to be scared about, something which could justify his fear.
Meanwhile, Clara and Danny are scared on their date - and that's why they each tried to sabotage it, they're scared of having a relationship. Clara realises through meeting young Danny that it's okay to be scared. Therefore, she finally acknowledges she is scared and is able to move past it, instead of it being a stumbling block between her and Danny on their date.
Now, the space thing, that's another example of the Doctor's subconscious. The whole thing is a subversion: It plays on what we already expect. If there's ever a program you expect to find one, it's Doctor Who. But this one didn't have any. We've been told for decades that monsters exist, and we expect to be shown one again. But this time we are shown something else: fear itself. So, after 700 years of living, he realises - or, at least, we see for him - that he is permanently scared. As he tells young Danny, you're aren't safe anywhere. We're presented with the psychological fallback of a guy who walks around believing aliens exist, and that they could be hiding in plain sight. He starts to believe they're there when they aren't.
Subconsciously, he's just afraid, but he has to justify it in some way, so he tries to convince himself that such things are hiding in plain sight. After all, this is a universe which has the Weeping Angels and the Silence. It sounds like there could be invisible monsters. He believes it. We - knowing what kind of show this is - believe it too. And that's the mistake both we and the Doctor make. We are aware of certain conventions.
I do think it should have been addressed explicitly in the episode, though. Instead of just leaving us saying, "Oh yeah, what was all that with the bedsheet?" Some people have said it will be addressed later in the series, and that's not fair, because it won't be. It should have been stated definitely that it was the power of his paranoia. Saying it was just 'nothing' is misleading, as the bedsheet DID move, but it did so with the power of an ancient Time Lord's subconscious. Some other people simply believe it was another kid - one of young Danny's friends - which means that the whole thing is misinterpreted. Of the 4.08 million who saw the episode, not everyone would have understood it, simply because it wasn't explained enough.
Thing is with some 'it doesn't matter' type loose ends is: like the spin top scene at the end of inception. we're told constantly that it matters - it's hammered into us until, finally, we're convinced it is - and then they say, "actually, it doesn't matter". It's a slap in the face to the viewer, because we've suspended our disbelief and bought into something, and then we're basically told we were fools to do that. Mofatt just about got away with it - but only because message boards were able to explain it and basically save his bacon.
Not sure I agree with him about the last part though, I'm perfectly alright with something not being directly explained, it makes it more interesting.
Makes me think of Pan's Labyrinth and the idea that all of the fantasy elements are in the girl's head, but there is never any logical explanation of how she got out of the room at the end.