This is an odd episode. It's another one that seems to want to mix humour in - with an opening joke about lowercase d-doctors, references to the cat nuns, and the "right angle parking" of the tardis bit. But it also goes into some dark topics - missing children, abusive parental relationships, loneliness. But none of it really comes together. The acting doesn't help - the kid actor is pretty bad, even by kid actor standards, and the dialogue on the TV news sequences is awkward. I'm also at a loss of what the story is even about - the aliens spend an eternal childhood in space, so they makeup their own imaginary worlds, which doesn't at all mesh with the SCP-085 plotline. The sequence with the doctor racing with the olympic flame is maximum cheese, and would be a great ending if it had been a "fun" episode all along instead of trying to also be serious. The ending feels pointlessly enigmatic, as if to telegraph "oh but travelling with the doctor is always a risk", but that was the whole point of the previous episode too so the writers are repeating themselves a bit.

Random note: It's supposed to be in summer for the olympics, but at times you can actually see their cold breath because they filmed in winter. They had doctor and rose comment on how cold things are to try and cover for this.