I realize it bothers me when the Doctor has friends we don’t know about.
Most of the time when the Doctor meets an interesting side character, it’s someone who’s already there when he lands and has a reason for being there: Jabe, Lynda, Nasreen, even Captain Jack. Vincent van Gogh, Charles Dickens, Agatha Christie are all found in situ. Only in a few cases, interesting people are plucked out of their natural setting and plopped into the Doctor’s story rather than the other way round.
‘Demons Run’ is the story that’s on my mind, but ‘Dinosaurs on a Spaceship’ also qualifies. I really like these characters, but I wanted more – not a detailed backstory, just something a little less handwavey, a little more than ‘wouldn’t this be cool.’ I guess it’s supposed to be mysterious, to imply that the Doctor has a busy off-screen life, but instead it just comes off as lazy.
I also for some reason don’t like Moffat’s bring-everyone-together episodes, and I’m not sure why. Vincent’s inclusion in ‘The Pandorica Opens’ bothers me, though Captain Avery’s appearance in ‘Demons Run’ doesn’t. I adore every minute of ‘Journey’s End,’ with all of RTD’s companions in one place, but the Moffat variants don’t have the same appeal. They just seem so random. In ‘Stolen Earth/Journey’s End,’ every character has a reason to be doing what they’re doing, based on what they’ve done before. In contrast, Vincent has no reason, and Vastra and Jenny have no ‘before.’ Avery’s appearance is somewhat more comparable to Martha’s and Sarah Jane’s: he’s just flying around out there, getting to know the cosmos, and he owes the Doctor his ship and his son’s life, so why wouldn’t he come when the Doctor calls?
The others just seem gratuitous. ‘Pandorica/Big Bang’ and ‘Demons Run’ feel like writers throwing all their toys in a heap without bothering to construct a story to put them there. ‘Demons Run’ and ‘Dinosaurs’ feel like writers trying to create mystery without bothering to actually create mystery. Davies threw all his toys in a heap in ‘Journey’s End,’ but he gave them a damn good reason. Even the ‘End of Time’ denouement, sappy as it may be, is rooted in motivations already familiar to the audience. The stories satisfy, and no one – viewer or character – is left hanging.