With Season 14,amoeba sisters video recap sex linked traits answers amoeba sisters video recap sex linked trait' Doctor Who showrunner Russell T Davies has been tantalizing new viewers with the inviting charisma of the Fifteenth Doctor (Ncuti Gatwa) and his chipper companion Ruby Sunday (Millie Gibson). But for longtime Whovians, these fresh adventures have proven to be rich with Easter eggs referring back to deep-cut show lore — and teasing exciting new possibilities. 

We've broken down the clues of "Space Babies"and "The Devil's Chord,"even digging deep into the emerging mystery of Susan Twist. Now, it's time to look into "Boom," a war-centered episode that features the return of former showrunner Steven Moffat as the ep's screenwriter. 

Here are all the Easter eggs we've found in Doctor Who's "Boom."

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Susan Twist returns.

Susan Twist as Tea Lady in "The Devil's Chord." Credit: Disney+ screenshot

The English actress has been popping up on British television since her debut on an episode of the cop drama The Squadback in 1980. But recently, she's been driving Whovians into fan-theory frenzies by appearing in four episodes of Doctor Who(and counting). Here, she pops up as the face of the artificial intelligence-powered ambulance, which seeks out combat situations and then administers help as it sees fit. Regrettably, that can lead to some very dubious employment of euthanasia. (RIP, John Francis Vater (Joe Anderson)). 

SEE ALSO: 'Doctor Who's Susan Twist mystery: Breaking down the clues and fan theories

In our thorough breakdown of Susan Twist's appearances on Doctor Who, we spin out the possibilities of what her curious repeated casting means. In "Boom," her character is the least human so far, and also the most deadly. 

"The Skye Boat Song" is sung.

The inciting incident of "Boom" is the Fifteenth Doctor stepping on a landmine. Thankfully, he has the presence of mind to freeze immediately, staving off its violent reaction. To keep himself calm, he sings, "The Skye Boat Song."

"Speed, bonnie boat, like a bird on the wing.

Onward, the sailors cry!

Carry the lad that’s born to be King

Over the sea to Skye."

"It's sweet and it's sad," Fifteen says of the song to Ruby. "And it's about soldiers fighting. But it's sad, like a lullaby." 

Dating back to 1782, this Scottish adaptation of a Gaelic song tells the tale of Prince Charles Edward Stuart, who, after facing defeat at the Battle of Culloden in 1746, narrowly escaped being captured by German soldiers. This detail could tie back to "Boom" in its sad story of soldiers at war.

Notably, the song has been previously employed on Doctor Whoback in 1968, when the Second Doctor (Patrick Troughton) played it on a recorder in "The Web of Fear." Take a listen: 

The moon and the president's wife get a mention. 

The Doctor and Ruby look each other while he's on a landmine in "Boom." Credit: Disney+

When "The Skye Boat Song" fails to cure the Doctor of his nerves, he tries another tactic, reciting a poem: 

"I went down to the beach

And there she stood, 

Dark and tall, at the edge of the wood.

'The sky's too big. I'm scared,' I cried. 

She replied, 'Young man don't you know there's more to life

Than the moon and president's wife?'"

Admittedly, we can't place the origin of this poem.

However, it does remind us of something Missy (Michelle Gomez) once said of the Doctor. In "The Magician's Apprentice" (Season 9, Episode 1), companion Clara (Jenna Coleman) asks the fascinating frenemy Missy how long she's known the Doctor. Missy replies, "Since always. Since the Cloister Wars, since the night he stole the moon and the president's wife, since he was a little girl. One of those was a lie; can you guess which one?" 

Later, the Doctor and Clara again speak of moons and presidential wifery in "Hell Bent," an episode in which Twelve convinces an armed squad of soldiers to drop their guns and join his side against a villainous president Rassilon. Retelling the tale to Clara, he touches on Missy's gossip with a correction. "That was a lie put about by the Shobogans. It was the President'sdaughter. I didn't steal the moon, I lost it." 

On a thread in the Gallifrey subreddit, a user suggests this line means the President's daughter is actually the First Doctor's granddaughter Susan, whom Fifteen mentions in "The Devil's Chord." Coincidence or clue? 

V for Villengard

John Francis Vater (Joe Anderson) is an Anglican Marine in "Boom." Credit: Disney+

The landmine the Doctor is standing on is made by Villengard, as he explains: "Biggest weapons manufacturer in recorded history. Supplied all sides in all conflicts for the past two centuries in this sector." He later adds, "War is business, and business is booming."

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This ties back to Doctor Who lore, in which Villengardis a planet known for weapons manufacturing. As a screenwriter, Moffatt has previously referred to Villengard in the two-part episode "The Empty Child/The Doctor Dances," then in "Twice Upon a Time," when it is found in ruins by the First Doctor (David Bradley) and the Twelfth Doctor (Peter Capaldi). 

But what Fifteen shares with Ruby is for focusing on this particular landmine from the Villengard: "I had to deactivate one of these [Villengard land mines] once. At a lesbian gymkhana. Underwater. For a bet. Except it wasn't live and I wasn't standing on it. And I lost that bet. Sorry! Wrong moment for this story!"

Steven Moffat found inspiration for "Boom" in "Genesis of the Daleks."

The Doctor stands on a landmine. Credit: Disney+

Talking to DoctorWho.tv,the "Boom" screenwriter said, "I had this idea of the landmine, which of course is a short sequence in 'Genesis of the Daleks' that I happened to love when I was a kid."

Broadcast in 1975, "Genesis of the Daleks" featured a scene in which the Fourth Doctor (Tom Baker) steps on a landmine and pauses before it explodes. In one tense sequence, his companion, medical officer Harry Sullivan (Ian Marten), saves him by placing rocks beneath it to stabilize the device. 

"I thought, 'What if you did it for a whole episode?'" Moffat continued. "The Doctor on a knife's edge, one wrong move and it's all over. It would take so much away from him; he can't run about, he can't bamboozle people, and he literally can't move. I thought, 'That's something that I haven't done.'"

"Dad to dad."

The Doctor holds Vater's casket. Credit: Disney+

Vater might be dead, but as his daughter Splice says, he's not gone. She means on a spiritual level. But within the episode, the Doctor talks to the AI slice of Vater swallowed up by the Villengard AI algorithm. The Doctor appeals to Vater, asking him to essentially hack the AI ambulance (played by Susan Twist) and save the day by de-activating the landmine, preventing the Doctor from becoming an accidental bomb that could blow up the whole planet.

In his plea, Fifteen says, "Dad to dad." So, who are the Doctor's children? 

The First Doctor canonically has 13 children. However, the Tenth Doctor (David Tennant) revealed in his run that the Doctor's children had all died in the Last Great Time War. But then came "The Doctor's Daughter," a Tennant-era episode in which the Doctor was unknowingly sampled with a progenation machine that birthed a twenty-something blonde and bubbly daughter dubbed Jenny, born to serve as a soldier — a vocation which the Doctor abhorred. Despite their differences, this father-daughter duo bonded to save the day. Then she took off on her own uncharted adventures. 

Bonus fun fact: Georgia Moffett, who played Jenny, is the real-life daughter of the Fifth Doctor, Peter Davison. And she married David Tennant after he played her father on Doctor Who. 

Here come the Anglican Marines. 

Anglican Marines look scared in "Boom." Credit: Disney+

Doctor Who is no fan of guns or war, so for much of the episode he mocks the Anglican Marines. Specifically, he chastises the soldiers for starting a war with smoke and shadows, blaming their religion. "Faith," he snarls, "The magic word that keeps you from ever having to think for yourself."

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To hammer the point home, he later issues a cynical "thoughts and prayers," suggesting it is up to them to save themselves. Prayers won't save them. But a dad dedicated to protecting his kid will. 

"Fish fingers and custard is my favorite." 

This bizarre snack is a callback to the Eleventh Doctor (Matt Smith). When the Doctor first met young Amy Pond (Caitlin Blackwood), he was desperate to find a food he would enjoy eating with his newly regenerated mouth. After a lot of failed attempts (yogurt, bacon, baked beans), the Doctor discovered his favorite snack to be fried fish fingers and sweet custard. 

"Boom" reveals the small but sweet detail the Doctor has maintained a taste for the funny food pairing. But it also might be that little Splice, orphaned by holy war, reminds him of his long-lost companion, Amy. 

Ruby's snow returns. 

Credit: Disney+

There's something special about Christmas foundling Ruby Sunday, and snow seems to be a clue. It fell the night she was born and left at a church on Ruby Road. It fell in the TARDIS when she was present, and in "Boom" it falls seemingly because she's been critically injured. (Such precipitation is a noted first for the planet.)

We're not sure yet what this means. But once Ruby is safe and peace restored, the Doctor says something curious about snow… and death.

"Dying defines us," he tells Ruby. "Snow isn’t snow until it falls." Does this mean Ruby is destined to die? And perhaps her fall will not be the end, but a new beginning? 

The Doctor breaks the fourth wall again. 

Splice talks to her dad. Credit: Disney+

When the Doctor delivers the snow line, adding meaningfully, "We all melt away in the end," you might think he's looking at Mundy and Splice, who stare off into the planet's horizon, a newly formed family. But while Ruby seems to be looking off into the mid-distance, the Doctor is looking straight into the camera, talking directly to the TV audience. 

"But something stays," he adds, as Vater's hologram waves goodbye. "Maybe the best part." 

The Doctor also broke the fourth wall in "The Devil's Chord,"as did Maestro. But before we can make sense of what all this meta business means, he continues talking to us with a bit of poetry…

"A sad little man once told me: What survives of us is love." 

This is the last line of the show, before a single snowflake flurries from the departing TARDIS. It is also the last line of the poem "An Arundel Tomb"by English poet Philip Larkin, published in 1954. The celebrated piece of poetry describes a monument in Chichester Cathedral, where the statues of a knight and a maiden lie on their backs, holding hands gently. Though the figures that inspired them are dead, their love lives on through this monument. 

The Doctor's remark suggests he's hung with Larkin at some point and values the idea that love lasts beyond death. What might this mean for the Doctor's lost children and granddaughter? 

Doctor Whostreams Friday at 7:00 p.m. ET on Disney+, where available,and simultaneously on May 11 at midnight on BBC iPlayer in the UK.

Topics Doctor Who Streaming