【To Be Twenty (Avere vent’anni)】

Doctor Who's second season on To Be Twenty (Avere vent’anni)Disney+ kicked off Saturday with "The Robot Revolution." The season arc revolves around new companion Belinda Chandra (Varada Sethu) — latest in a long tradition of reluctant (or "kidnapped") companions aboard the TARDIS.

But that's just the surface level of an episode that contains a surprising number of homages for all its shiny newness, and a real-life story behind the scenes that changed Belinda's very name. Let's dig in!

How Belinda got a star (and planet) named for her.

The International Star Registry is one of many real-life companies claiming to give you naming rights for objects in space. Given that its services have been used to name stars for Queen Elizabeth II, King Charles III, and Princess Diana, this American company may be more well-known in the UK now.

So popular, Whoshowrunner Russell T Davies tells Mashable, that they had to change her name three times to find one that wasn't already in the registry: "She was originally going to be Belinda Finch!"

Belinda's one-time boyfriend Alan used a fictional version of the service to name a star for her, pointedly adding the "Miss," no matter what she thinks of the designation.

But actually having the star (and the habitable planet around it, and its colonists) take the name MissBelindaChandra, no matter the dubious effectiveness of the registry's names, and demanding she be the planet's queen? That's a plot twist worthy of Douglas Adams. Which is entirely appropriate, because ...

Belinda's outfit is a sci-fi (and Doctor Who) tradition.

Belinda Chandra is not (yet) the best-known fictional Brit to be yanked away from Earth before they've had a chance to change out of robe and PJs. That would be Arthur Dent in TheHitchhiker's Guide to the Galaxy(played by Martin Freeman in the movie, and Simon Jones in the radio and TV series). Unlike Belinda, who gets a costume change in the next episode, Arthur's robe becomes his outfit for his entire time-and-space adventure.

Since Hitchhiker'sauthor Douglas Adams was also once a Doctor Whoscript editor, it seems appropriate that the show is referencing Arthur's nightwear — for two episodes running. Check out what the Doctor was wearing at the start of the Christmas episode "Joy to the World"; not an exact match for Arthur's robe, but clearly a loving homage.

Those robots look familiar.

Both the robots' 1950's-style rocket (very similar to one that appeared in the first Disney+ Doctor Who special "The Star Beast" in 2013) and the robots themselves may spark memories in fans old and new.

The robots' emoji-like faces are somewhat similar to the deadly robots in "Smile" (2017), also set on a planet of space colonists terrorized by their machines. "Smile" was also the first outer-space voyage for a new Whocompanion — in this case Bill Potts (Pearl Mackie), doomed friend of the 12th Doctor (Peter Capaldi).

Older fans may also spot a storyline that's reminiscent of "Robots of Death," (1977) a classic from the Tom Baker era:

Where we've seen the Doctor's hearts before.

We've known the Doctor (and by extension, every other Time Lord) has two hearts ever since 1970, when the newly regenerated Third Doctor (Jon Pertwee) was taken to hospital and given an X-ray in "Spearhead from Space." We've learned little bits about how this strange physiology works ever since; in "Smile," Capaldi's Doctor admitted two hearts means he has "really high blood pressure."

But the stunning scene when the Doctor holds up the live X-ray blanket to show Belinda his hearts is only the third time we've actually seen them since "Spearhead from Space" (the others, also both X-rays, were in the 1996 TV movie starring Paul McGann, and the 2005 story "Dalek" starring Christopher Eccleston) — and the first time we see them actually beating. Great news for any Whovian cardiologist who wants to examine the Doctor's blood pressure problem!

This isn't the Doctor's first AI encounter.

Oh, you've been worried about out-of-control self-aware AI taking over the planet for the past few years? Try 59 years. The Doctor has been dealing with self-aware machine intelligence since "The War Machines" (1966), when his first incarnation (William Hartnell) defeated WOTAN, which stands for Will Operating Thought ANalogue. Not quite as snappy as "AI," but you get the idea.

Doctor Who didn't actually use the words "artificial intelligence" or "AI" until "Death in Heaven" (2014), when Missy (Michelle Gomez) told an "AI interface" to "kindly delete your opinions." But it's made up for lost time by trotting out the words or the acronym in eight stories since.

• 'Doctor Who' season premiere review: 'Robot Revolution' makes us reluctant companions
• 'Doctor Who' Season 2 trailer introduces new companion, Eurovision spoof, and more
• 'Doctor Who' returns — now with Alan Cumming!
• 'Doctor Who's 'Joy to the World' is a Christmas treat, bitter and sweet
• 'Doctor Who' showrunners on how 'Ode to Joy' paves the way for next season

Belinda isn't the first nurse on the TARDIS.

Belinda Chandra may have decided to call herself "The Nurse" in the style of the Doctor, but she isn't the first member of her profession to travel with him in time and space. That would be Rory Williams (Arthur Darvill), who traveled with wife Amy Pond and the eleventh Doctor (Matt Smith) in the early 2010s.

So shouldn't Rory have noted what horrified Belinda at the end of "Robot Revolution" — that scanning her with the Sonic Screwdriver without her consent violates basic medical principles? Different eras, different motivations, Whoshowrunner Russell T Davies tells Mashable; Rory is primarily "focused on fighting for the love of a good woman."

Meanwhile, at this stage, Belinda knows nothing but her job: "She'd be signing nondisclosure agreements all over the place," Davies says, noting that this is the first consent discussion of any kind in the show. "What's lovely about that moment is she pushes the Doctor into an apology. That's not something you get very often." (Fact check: true.)

We've seen Belinda's face before.

Why is the Doctor scanning Belinda's DNA anyway? To confirm his hunch that she's the ancestor of a soldier in the far future of last season's episode "Boom!" That would be Mundy Flynn, also played by Varada Sethu.

Will the DNA connection matter as the Doctor learns more about his mysterious new reluctant companion, or is that the only mention we get of a case where the double casting appears to be entirely accidental? Stay aboard the TARDIS to find out.

Doctor Who Season 2 premiered Apr. 12 on Disney+ and BBC.