Having established the new series of Doctor Who as being a place of aliens and time travel, just like the classic series, Russell T Davies chose to devote the eighth story of Season 1 to exploring the emotional consequences of time travel for one of the Doctor's companions, and in doing so, added greater depth to both of the show's lead characters.

It also set the template for the future of the show, with new companions often bringing their families along for the ride.

Here are a few things that you should keep an eye out for, the next time you watch. (The episode is available on iTunes and Amazon.)

"Father's Day" was one of Russell T Davies earliest ideas for the new show, having submitted a pitch in 2003 that contained the story he then called "Rose's Father." In the original pitch, Rose would observe her father's death while Judy (the name then given to Rose's mother Jackie Tyler) would tell the story of Pete Tyler's life and death to the Doctor in 2005.

This is Paul Cornell's first script for Doctor Who, having made his name with various Doctor Who novels, including "Human Nature," which he later rewrote as the Tenth Doctor two-parter "Human Nature" / "Family of Blood." Davies' original story had no extra-terrestrial presence, so Cornell introduced the flying monsters, calling them Reapers. He wanted them to look like the Grim Reaper (something close to Harry Potter's Dementors, only with scythes too). The production house The Mill, who designed the Reapers, made their tails scythe-shaped, in a hat-tip to the original concept.

The idea that a person who travels back in their own timeline should not touch their previous self (even if they are a baby) was first established in Doctor Who back in 1972's "Day of the Daleks." It was even given a name: the Blinovitch Limitation Effect. It appears again in the Fifth Doctor story "Mawdryn Undead," with the Brigadier meeting himself and setting off a huge charge of energy.

Should you wish to have a complete list, the name of the young man driving the Vauxhall Chevette that kills Pete Tyler (according to the script) is Matt.

https://www.youtube.com/watch?v=EaBQ0HG4HoA

"Father's Day" is only the second story in Doctor Who history to have shown a Doctor interacting with a version of himself (ie. not a previous incarnation) from the past. The first was "Day of the Daleks," in which the Third Doctor is seen tinkering with the TARDIS and chatting to his assistant Jo Grant, when a door opens and the Third Doctor and Jo Grant arrive from another point in the same story. Needless to say the TARDIS is not impressed.

For a story devoted to Rose Tyler's discovery that her dad is both not the heroic wonder-man her mother has always painted him as being, and also actually rather lovely and devoted to his daughter all the same, it pains us to reveal that Shaun Dingwall, the actor playing Pete Tyler, was less than gentle with the prop baby used to portray young Rose. Paul Cornell told Doctor Who Confidential that he took to practicing soccer tricks with it—balancing it on his feet, playing keepy-uppy—in between shots.

The message "Watson, come here, I need you" is heard on everyone's mobile phones. The Doctor says it's the first thing ever said over a telephone, Alexander Graham Bell's message to his assistant, Thomas Watson. However, his actual words (according to Watson's journal at least) were "Mr. Watson, come here, I want you." In the audio commentary for this episode, producer Phil Collinson says he thinks the error (which was not in the script) occurred when the line was re-recorded after the original voice actor had delivered Bell with a Scottish accent that was felt to be a bit stagey.

There's some temporal Rick-rolling going on when Pete Tyler drives Rose to the wedding back in 1987. Rick Astley's "Never Gonna Give You Up" is knocked from the airwaves by "Don't Mug Yourself" by The Streets, a song that came out in 2002. Clearly there's a message for Rose Tyler in the song's title, especially as it would have been out for three years before she even met the Doctor.

https://www.youtube.com/watch?v=veAIHDGghP4

As Sarah the bride arrives, her bridesmaid Suzie tells her very few people have arrived for the ceremony, adding that "there's no one from The Lamb and Flag." As a pub name, The Lamb and Flag is not tremendously common, but it derives from illustrations of the Gospel of John (1:29): "Behold the Lamb of God, which taketh away the sins of the world." Jesus, the Lamb, is commonly seen carrying a flag of St. George.

This image is the symbol of the Knights Templar, the military and financial order created in the Middle Ages during the Crusades. And, in a bizarre moment of cross-referencing that could be entirely accidental, the main pub featured in the Rik Mayall and Adrian Edmonson sitcom Bottom was also named The Lamb and Flag.

Paul Cornell was nominated for a Hugo Award for Best Dramatic Presentation, Short Form for "Father's Day," and again two years later for "Human Nature." Both times he lost out to Steven Moffat, who won in 2006 with "The Empty Child" / "The Doctor Dances," and in 2008 with "Blink."

Cornell was also nominated for Best Graphic Story in the 2014 Hugos for Doctor Who Special strip "The Girl Who Loved Doctor Who," making him the only writer to be nominated in two distinct media categories for Doctor Who (so far).

NEXT: 10 Things You May Not Know About ‘The Empty Child’

Now read the rest of the 10 Things You May Not Know About Doctor Who archive.