Doctor Who Series 10: 11 Easter Eggs & References In 'Oxygen'
1. The Doctor's Yo-Yo
When back at his office at St Luke's at the end of the episode, the Doctor plays with his yo-yo (no, that's not a euphemism, you depraved individual you).
This is the latest sign that the Twelfth Doctor has inherited a love for the simple art of yo-yoing from his Fourth incarnation. Tom Baker's Doctor was often seen with a yo-yo in his hand (hey, I said stop it), across nine separate stories at our count. This is the third time Capaldi's version has played with the toy.
He previously used it to test the levels of gravity when he landed on the Moon in 2014's Kill the Moon, just as the Fourth Doctor did in 1974's The Ark in Space.
What other Easter eggs and references did you spot in Oxygen? Let us know down in the comments.