This is Davina McCall's second appearance in the show, and the first time she appears on-screen. She previously voiced an android version of herself called the Davinadroid in the episode Bad Wolf (2005).
The department store that Ruby goes past is Henrik's, which was previously featured in the episode Rose (2005). It's the same store in which Rose Tyler had worked.
The Doctor mentions he learned to escape from handcuffs from Harry Houdini. While not seen on screen (though he's namechecked by the Third Doctor in "Planet of the Spiders"), Harry Houdini has met multiple incarnations of The Doctor in expanded media. He met the Fifth Doctor in the audiobook "Smoke and Mirrors", the Sixth Doctor in Harry Houdini's War (2019), an episode of Doctor Who: The Monthly Adventures (1999-2021), the Eleventh Doctor in the short story "Houdini and The Space Cuckoos", and the Twelfth Doctor in the comic strip "Theatre of the Mind".
A system transmitting information by rope knots, just like in the goblin ship, has some basis in reality. In the ancient Incan empire, quipu (or khipu) is a system of different knots tied in ropes attached to a longer cord.