With nearly sixty years behind it, Doctor Who is one of the longest-running shows. As such, it's understandable that it introduced many fan-favorite characters over the years. A lot of them went on to become the Doctor's companions, friends, or enemies, but some heroes left a strong mark on the show despite the fact they only appeared once.

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Mostly it happened because the character was well-written, had a strong storyline, or was played by an excellent actor. Sometimes, all of these factors are combined. It's unlikely the show will bring any of these one-off characters back but that doesn't change the fact the fans of Doctor Who would love to see them at least one more time.

10 Sally Sparrow

Sally Sparrow faces the weeping angels in Doctor Who

Doctor Who has several could-have-been companions, but Sally Sparrow is one of the most popular ones among the fans. Played by the talented Carey Mulligan who went on to star in multiple successful movies, Sally is a pleasantly down-to-Earth charming, intelligent young woman who doesn't lose her head even when she's distressed.

At the same time, she's not perfect as she has the tendency to keep her distance from other people. It helps that the episode focuses on Sally and the Doctor has only minimal space in it, so the audience has the chance to get to know her better. It'd be interesting to return to Sally a few years later and see how she moved on with her life, who she became.

9 Jenny

Doctor Who Jenny

Jenny's existence came as a surprise to the Doctor since she's his daughter and the Doctor originally had no idea he had children! Jenny was cloned from the Tenth Doctor's DNA, seemingly died at the end of her episode but then revived, took a ship, and traveled to space, presumably to go on many amazing adventures, just like her father.

Jenny's space adventures could theoretically start a brand new spin-off show of Doctor Who. Perhaps the Tenth Doctor could also make a brief appearance on the show. What would make it even more interesting is that in real life, David Tennant (the Tenth Doctor) and Georgia Moffett (Jenny) are married!

8 Jethro Cane

Doctor Who Jethro Cane

While the rebellious Jethro Cane didn't have that much space in the show, he still managed to attract attention. It helps that he was played by Colin Morgan who later went on to star in Merlin as the titular immortal sorcerer.

It's hard to imagine how would Jethro cross the Doctor's path again but in the world of Doctor Who, nothing is impossible. What's certain is that Morgan's fans would appreciate the opportunity to see an older (wiser?) Jethro in the show again and perhaps even find out how the difficult relationship between him and his parents evolved.

7 Idris

Doctor Who Idris

The Doctor is in luck when it comes to meeting extraordinary people. And one of the most unique beings was Idris, a woman with the TARDIS in her head. Needless to say, Idris was both a bit confused, brilliant and eccentric. She caused a lot of chaos which is something the TARDIS normally does as well when she brings the Doctor somewhere where he's needed, not where he originally wanted to go.

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It wouldn't be the first time a spaceship would gain a body, as it happened not only in Doctor Who but also another time-travel show, DC's Legends of Tomorrow, for example. If the Doctor is ever in need of a companion for another surface-bound adventure, Idris has what it takes to fight by his side.

6 Joan Redfern

Doctor Who Joan Redfern and the Doctor kiss

Joan Redfern is the one woman the Doctor could have been happy with had he only stayed human. Joan worked as a school nurse and appeared in the third season, in two episodes - Human Nature and Family of Blood. She and the Doctor fell in love when the Doctor believed he was a human named John Smith thanks to the chameleon circuit.

Joan then realized she had to let him go in order to save the world. Their romance never had a happy ending but it would be nice to see the intelligent and brave Joan one more time. Perhaps the Doctor could visit her moments before her death or in a more cheerful scenario, he could crash her wedding. As it's known that Joan got married and had children since the Doctor met her great-granddaughter, a writer Verity Newman, years later.

5 Astrid

Doctor Who Astrid

Not all singers can also pull off acting roles but Kylie Minogue managed it when she appeared as Astrid, a worker on the space ship Titanic. A crisis came, the Doctor saved the day, but Astrid died.

She was a kind and brave woman who treated others with respect and fought to help the Doctor. Plus, they shared a sad kiss at the end when it was clear Astrid wouldn't make it. Bringing her back would be difficult because of her death but in a world of time-travel, the Doctor could surely figure out a way.

4 Reinette Poisson

Doctor Who Reinette

Reinette is by far one of the most celebrated would-be companions of the modern Doctor Who. Some fans even prefer her over Rose Tyler who was traveling with the Tenth Doctor at the time. Reinette was a charming, funny, and intelligent young woman who was curious about the world and wanted to see the stars.

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Unfortunately, she died before the Doctor could come back for her. Sophia Myles, who played Reinette, and David Tennant had a natural chemistry, and thanks to the way Reinette was written, as well as Myles' acting chops, Reinette could still be an amazing companion even to another regeneration of the Doctor.

3 Adelaide Brooke

Doctor Who Adelaide Brooke

Defying the Doctor takes a lot of courage for good people but Captain Adelaide Brook managed it. After losing Donna and being alone, the Doctor snapped and decided to change history, consequences be damned. To stop him from becoming the Time Lord Victorious, Adelaide took her own life.

Before that, she was tough, intelligent, and brave, all of which made her instantly likable. It also helped that she was played by Lindsay Duncan, one of the most talented British actresses. Bringing back Adelaide from the dead would lower the value of her sacrifice but the show could always return to her career as an astronaut before the fateful events in The Waters of Mars.

2 Grace Holloway

Doctor Who Grace Holloway

The Eighth Doctor played by Paul Gann, drew a short straw. He never got his own season, let alone more, unlike the rest of the Doctors. And his movie wasn't accepted well by the general public. However, both the Doctor and his temporary companion Grace Holloway were sympathetic.

Grace worked in a hospital, she was intelligent, inventive, and not afraid to call out the Doctor's bluff. She also set out an example to the future companions since she and the Doctor kissed. That was something that was unusual before and became a lot more common since then. Bringing Grace back to the show would create a bridge between the Eighth Doctor's era and the regenerations that came after him.

1 The War Doctor

Doctor Who War Doctor

Unfortunately, one of the best one-off characters can't return, at least not with the same face. Actor John Hurt, who played the War Doctor, the hidden regeneration of the Doctor, passed away in 2017.

Despite only appearing once as the Doctor who had to make a horrible decision, Hurt immediately made the audience interested in the character. His talent gave a lot of gravitas to the role and it's unfortunate the War Doctor never got more space.

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