Idea Proposed and Used to Death during the New Series: Alan pointed out the other day that pretty much every episode this half-season has been ripping off The Doctor's Wife one way or the other. I'd say it's a bit early to begin recycling it, but it did wind up held over for a year, so maybe not.
Central Premise Recycled From: The Mind Robber crossed with Amy's Choice and squeezed into the B-plot of The Doctor's Wife, via the New Adventures novels (in which, early on, Ace got left behind by the Doctor and picked up somewhat later, during which time she'd turned into an embittered warrior woman). Though mind you, that could describe this whole half-season so far.
Reference to Moffat's Back Catalogue: Duplicates, Amy duplicates, get 'em while they're hot. Plus wibbley-wobbly-timey-wimey stuff again, and Amy Having Issues about her relationship with Rory versus her relationship with the Doctor. "Duck." One character's timestream moving at a different rate to the other's.
Amy Screws Up the day with Wuv: Well, it's more like "everybody else screws things up out of Wuv for Amy," but she's central to it anyway.
Joss Whedon Called...: He wants both his kick-ass warrior woman and a plot based around a person working against their own doppelganger/alt-universe/future self back.
And from Lawrence Miles: Different characters experiencing time in different ways? Hello, The Judgment of Sutekh.
Murray Goldwatch: Pretty good this week; Gold is always best when he's going all introspective and Bear McCreary with the bells and percussion.
Nostalgia UK: Those robots were straight out of The Hitchhikers' Guide to the Galaxy film, and a quarantine facility cum leisure park is a rather Adamsesque/Red Dwarf sort of idea.
Inside Jokes: The Doctor's proclivity for taking his companions to rather dangerous leisure planets is well established.
Teeth! No, though robot-Rory has a fetching smile.
Hats! Old Amy's chapeau.
Fish! There's an aquarium, though we never get to see it.
Small Child! No, though everybody's likely to think the title refers to little Amelia.
Item Most Likely to Wind Up as a Toy: The robots obviously, though there might be a market for a limited-edition Amy Pond Up the Menopause.