Are you ready for the worlds of Bridgertonand Doctor Whoto collide? The trailer for episode 6, "Rogue," reveals that the Fifteenth Doctor (Ncuti Gatwa) and his mysterious companion Ruby Sunday (Millie Gibson) will touch down for an adventure in Regency-era England, the same time as the popular Netflix romance series. But it's not just this temporal setting that the two English series have in common. 

"Oh my Bridgerton!" Ruby squeals in the Season 14 trailer. This exclamation determines that the Shondaland series based on Julia Quinn's romance novels exists in the world occupied by Ruby and her Doctor. But if that's the case, then how can cast members of Bridgerton be popping up on Doctor Who as other characters? 

The likes of Jonathan Bailey, Adjoa Andoh, and Claudia Jessie appeared on Doctor Who before Bridgerton got a shout-out on the sci-fi series. Just this season, the glorious Golda Rosheuvel, who plays Queen Charlotte in Bridgerton, joined their ranks, appearing in "Space Babies"as the harried Nan-E. And Season 3's leading lady Nicola Coughlin has been announced as a special guest for this year's Doctor Who holiday special, meaning another Ton resident will be getting tangled with a Time Lord.

Asked for a timey-wimey explanation for such meta crossovers, Season 14 showrunner Russell T Davies told Mashable, "It's an amazing universe where these doppelgangers keep appearing!" 

Doctor Who collides with Bridgerton, EastEnders, and Kylie Minogue! 

Davies noted that the popular British soap opera EastEndersalso exists in the Whoniverse, but that hasn't stopped a slew of its cast— including Bonnie Langford, Davood Ghadami, and Nina Wadia, to name just a few — from popping in for adventures.

"I'm quite sure the Doctor has spoken of Kylie Minogue a couple of times," Davies continued, adding, "And it's actually our best, highest-rated story ever in history is with Kylie Minogue." 

Famously, the Australian pop icon starred opposite David Tennant's Tenth Doctor in "Voyage of the Damned,"one of the best — and most gutting — holiday specials the series has yet to air. But prior to playing the beautiful and doomed Astrid Peth,Minogue had been referenced in the Tennant ep "The Idiot's Lantern,"in which the Doctor referenced her song "Never Too Late," saying, "It’s never too late, as a wise person once said. Kylie, I think."

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Timey-wimey casting is part of Whoniverse rules. 

Davies won't be bothered by fans calling out the confusion of Rosheuvel appearing in Season 14 while Bridgerton is mentioned just a few episodes later. For one thing, Doctor Who has been at this game for a while. After all, it's a massively influential series that's been on for decades. Of course, famous UK stars are bound to pop up again and again. But as was the case with Peter Capaldi — who went from seemingly doomed Pompeii resident to the Twelfth Doctor — sometimes a sci-fi plotline can come into play as explanation. 

Davies told Mashable, "It's just a strange universe. I came up with a phrase for that in one episode: spatial genetic multiplicity." 

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Davies coined the term for when actress Eve Myles popped up across the Whoniverse, first as servant girl Gwyneth in "The Unquiet Dead" (the relaunched Season 1, episode 13), then as police officer Gwen Cooper on the spinoff series Torchwood. 

"In the end," Davies said with a grin, "I just gave a big shrug and said, 'That's spatial genetic multiplicity." Essentially, in a vast universe of time and space where anything can happen, sometimes unrelated people look like actors or characters you've seen before. Sometimes it means nothing. 

Sometimes, however, Davies is laying down so many Susan Twistcrumbs that fans can't stop speculating. 

How to watch:New episodes of Doctor Whodrop every Friday night at 7 p.m. ET on Disney+, where available, and simultaneously at midnight on BBC iPlayer in the UK. The season finale airs June 22.