When Mr. Halpen and his group arrive on the planet and are first entering the building, the Jupiter 2 spaceship is seen in the background.
Solana Mercurio says to an Ood with the "Comedy Classic" setting on its Translator Ball, "Ood, you've dropped something." The Ood replies, "D'oh!" with the voice of Homer Simpson.
Numerous clips are shown from this episode.
Flashback is shown of Donna with the Ood.
Clip of Ood Sigma foretelling the end of the Doctor's song.
Flashback of the Ood.
Clip of the Doctor and Donna jumping clear of an explosion.