Arguably the best Doctor of all time, David Tennant is, to many, the face of Doctor Who. He showed commitment to the role that has seen his return to the series across various media and was provided a huge departure arc that coincided with us losing the incredible writing of Russel T Davis.

Within his three seasons (and multiple special episodes) there were various Easter eggs hidden within episodes. Some of these were pretty obvious, but a few were hidden beneath some hard-to-crack layers.

International Electromatics

Way back in 1968, an episode called ‘The Invasion’ introduced us to a company called International Electromatics. They were run by a guy called Tobias Vaughn, who helped the Cybermen invade earth.

A little Easter egg references them through a season two episode which sees Cybermen rising up in the parallel universe. The fake company used to recruit homeless people as Cybermen is also called International Electromatics.

‘Something Of A Wolf In You’

‘Tooth And Claw’ is the second episode of season two, just the third outing we’d ever had with the Tenth Doctor. It also used a guest visual effects artist to convincingly create werewolf hair.

Anyway, there is a subtle Easter egg in one particular line of dialogue in which Sir Robert tells Rose that there is “something of the world about you”. This is certainly a call-back to Bad Wolf.

Merry Christmas, Doctor

It takes a lot of time and money for a TV show to get the rights to a song, especially a well-known classic like Slade’s ‘Merry Xmas Everyone’ from 1973. The Doctor Who team obviously managed it, though, because it shows up in a lot of the Doctor Who Christmas episodes.

While this persists beyond the time of the Tenth Doctor, it was his episode ‘The Christmas Invasion’ that first created the trend.

‘I Don’t Like It’

It was an understandably huge event when David Tennant (and Billie Piper, though we never got to see them interact, boo!) were brought back into Doctor Who for the 50th-anniversary special.

Tennant is brought into the TARDIS by Matt Smith’s Eleventh Doctor and he exclaims “I don’t like it”, in reference to the update his time machine had had since he was last in it. This was an Easter egg for particularly devoted fans who remember the reaction of the Second Doctor to his updated machine following his regeneration.

Dalek Tommy Guns

With Torchwood taking off at the same time as David Tennant’s Tenth Doctor had us on the edge of our seats, it was no surprise that we’d see the two shows overlap in some way, at some point.

During ‘Daleks In Manhattan’, we see people holding Dalek Tommy guns, which is a weapon we can see exist in the Torchwood world, too. This is a subtle reference but proves an eye for detail (and an eye for recycling props) connecting the two shows.

Sydney Newman And Verity Lambert

The two people responsible for Doctor Who existing in the first place are Sydney Newman and Verity Lambert. Newman actually created the show in 1963, bringing it to the BBC and creating an inimitable phenomenon. The producer he got on board was Verity Lambert, the youngest and only woman producing at the BBC at the time.

These two incredibly important visionaries were given a shout out during season 3, where the human version of the Doctor explained that his parents (who didn’t actually exist) were named Verity and Sydney.

The Mysterious Sarcophagus

In the 1975 episode ‘Pyramids Of Mars’, there is a huge sarcophagus just outside the entrance to a pyramid. When Rose gets out of the TARDIS at Torchwood during the ‘Army Of Ghosts’ episode, we see a massive sarcophagus that looks identical to that one right next to her.

While it makes you wonder where the props department got their hands on a sarcophagus to use for half a second, it is still a very cool call-back to an episode more than thirty years old.

The Bad Wolf Virus

‘Love & Monsters’ was a pretty controversial episode of Doctor Who. In short, it took The Doctor and Martha out of the action, and left Peter Kay to play the bumbling Abzorbaloff and Marc Warren as Elton Pope. It was a strangely comedic, weirdly irrelevant episode that fans either loved or hated.

Whichever way you look at the episode as a whole, it did include yet another subtle reference back to Bad Wolf. In the episode, it is explained that Torchwood lost its files to the Bad Wolf virus. This begs the question of whether this was a literal computer virus or Rose’s actions as the Bad Wolf caused some sort of electromagnetic issue that actually wiped computer memory.

This particular Easter egg follows more traditional definitions of the word than placing one in an episode. If you have access to the series three box set DVD then follow these instructions: insert disc 4, select ‘scene selection’ on the episode ‘Blink’, press the up button when you’re hovering over the scene called ‘keep looking’, which should then highlight the actual episode name.

If you click ‘ok’ on that, you’ll see The Doctor giving his message to ‘not blink’ straight to you!

Alonzy Alonso!

During ‘The End Of Time Part 2’, The Doctor made sure to visit all of his companions one last time, just to make sure they were doing okay. He found Captain Jack Harkness in a bar filled with aliens. Many of these were Easter eggs in themselves, with the likes of the Hath enjoying a drink. The Doctor hands Jack a note saying, “his name is Alonso”, referring to the guy sitting near Jack.

At first, it seems like The Doctor is just helping his friend out on a night out, but if you have a good memory, you might remember Alonso from somewhere else. In the Christmas special ‘Voyage Of The Damned’, he is introduced as a worker on board the Titanic. This is a very nice way to reference and episode fans might have forgotten about.