Doctor Who Series 10: 12 Easter Eggs & References You Might've Missed In "Knock Knock'

The Doctor decides to call these alien woodlice "Dryads" as he doesn't just want to call them "lice." The Doctor has a history of picking his own made-up-but-clever-sounding terms for things. Back in The Girl in the Fireplace, he calls the aforementioned revolving fireplace a "spatio-temporal hyperlink." He then admits he made this up on the spot to avoid saying "magic door."

Dryads, by the way, are creatures from Greek mythology. They are spirits who live within oak trees. They are usually depicted as beautiful, ethereal women, however, not creepy-crawlies.