If bringing back Davros wasn't enough of a callback to the Doctor's past, the show made sure to make some explicit references by including clips from past episodes during a scene between the pair of old enemies. There's the Fifth Doctor in Resurrection Of The Daleks, the Sixth Doctor from Revelation Of The Daleks, the Seventh in Remembrance Of The Daleks, and the Tenth in Journeys End and, for some reason. Most notably, though, are a couple of clips of Tom Baker's Fourth Doctor and Genesis Of The Daleks, which the opening two-parter of Series 9 paid serious homage to. Then there were the Daleks themselves. The return to Skaro brought with it all manner of the oversized pepper shakers, including the bronze ones from the revived series, ones from the 70s and 80s, a special weapons version, and even the Supreme Dalek. Any lingering annoyance at the multi-coloured ones introduced a few years ago may have just dissipated with this episode.