The 7 best Easter eggs and hidden references in this week’s Doctor Who

Alpha Centauri

Yep, that strange eye-creature welcoming the Martians into intergalactic society was none other than Alpha Centauri, an ambassador and friend of the Doctor who previously appeared in classic Ice Warrior stories The Curse of Peladon and The Monster of Peladon, in 1972 and 1974 respectively, alongside Jon Pertwee’s Time Lord. You can read more about the character and their triumphant return here.

Amazingly, original voice actor Ysanne Churchman was also brought back to provide Alpha Centauri’s dialogue, and the whole thing was a brilliant surprise to top off the episode – assuming, of course, that you didn’t spot the clues in a special Radio Times preview picture a couple of months ago…

The Galactic Federation

Bundled in with Alpha Centauri, the end of the episode also introduces the Ice Warriors to the concept of the Galactic Federation, an organisation that appeared in both Peladon stories as a political entity intended to ensure peaceful relations between all the various species in the galaxy after the collapse of the Earth Empire.

The Federation hasn’t been mentioned in the TV series for a while, but it did recently crop up in a tie-in novel for the current series of Doctor Who called Diamond Dogs, written by Mike Tucker.

Queen Victoria

In a small but nice detail that might have passed some fans by, the portrait of Queen Victoria that the British Army soldiers have in their camp isn’t the real Victoria at all – rather, it’s the version of her played previously by actress Pauline Collins in Russell T Davies’s 2006 Doctor Who episode Tooth and Claw (below).

After all, this 1881-set story is only a couple of years after the former’s 1879 timeframe, so it makes sense that she’d look the same (even if she is a secret werewolf).

Catchlove

If you were impressed by the brilliant naming of dastardly villain Neville Catchlove (Ferdinand Kingsley) in this week’s episode, then you have history to thank – because Mark Gatiss recently revealed that the character was named after a real soldier who cropped up in a book he read for research.

“I did a lot of reading again as I always love to do around the notion of the Empire and colonies,” Gatiss told RadioTimes.com and other journalists.

“There’s a really wonderful book I read called Running the Show, which is where I got Catchlove's name from. It’s all about the men, and they were only men, who ran the Empire.”

Specifically, we’re pretty sure that he’s referring to a soldier mentioned in Stephanie Williams’s history book called Edward Napolean Buonaparte Catchlove who was actually alive (though older and in a very different situation than the TV Catchlove) at the time Empress of Mars is set.

We understand why Gatiss went for Neville for his version, though – even for Doctor Who, the real Catchlove’s name might be a little extreme…

Zulu

Speaking of that time period, it’s worth noting that the entire episode is something of an homage to classic 1964 film Zulu, which depicted the real-life 1879 battle of Rorke’s Drift between 150 British soldiers and 4,000 Zulu warriors and starred Michael Caine and Stanley Baker.

“It is Zulu with Ice Warriors, as it were,” Gatiss told us. “That's my pitch.”

Of course, Empress of Mars is set just two years after this real-life battle, and it turns the conflict on its head by making the Ice Warriors the outnumbered yet more militarily advanced force who successfully defend their position from a greater number of foes with less powerful weaponry – in other words, making the British take on the role of the Zulu warriors in this new conflict.

Ice Hives

Obviously, one of the most noticeable callbacks in this episode are the Ice Warriors themselves, a classic series species who appeared in four Doctor Who stories in the 1960s and 1970s before being brought back in Gatiss' 2013 episode Cold War (you can read more about their history here).

This time, the writer fleshes out their backstory a lot more, revealing that they have a Queen and exist in Hives – but this isn't the first time that the latter detail has been mentioned in the series, with 2014 episode Robot of Sherwood (also written by Gatiss, who must have had the idea for a while) featuring the Doctor's offer to take companion Clara (Jenna Coleman) to Ice Warrior Hives on Mars. He got there eventually!

Sleep No More

Gatiss recently revealed that his first idea for an episode this year was a sequel to 2015 story Sleep No More, which saw monsters formed from rheum on a sleep research station terrorise humanity.

"Although it was still in space, [Sleep No More] was originally going to be on a trading floor,” Gatiss said at the time. “It was a stocks and shares thing, with these executives who were trying to stay awake in order to be more productive.

“And then it sort of changed into the sleep research station [of the finished episode].

“I thought there was something in that, and actually maybe I could do a modern day one, set in the City,” he added. “Where they'd invented the same process but actually thousands of years earlier, and it had the same effect.”

In the end, Gatiss went in a different direction to create Empress of Mars’s Victorian Ice Warrior adventure – but a little callback to Sleep No More still made it to the screen, with that episode’s title repeated by Ice Queen Iraxxa (Adele Lynch) as the rallying call to awaken her Ice Warrior army: "Sleep no more!"

Doctor Who continues on BBC1 next Saturday 17th June at 6:30pm