Harry Potter and Doctor Who are both very successful. They are both entertaining and helped form the childhoods of many people, and both timeless stories are still being introduced to many even in adulthood. Harry Potter and The Doctor are two of the most beloved fictional characters in the world.
Although one is a magical film series based on the novels by J.K. Rowling and the other is a science fiction television adventure series, they have more in common than meets the eye.
The Conflicted Hero
Harry didn't ask to be The Chosen One. The Doctor didn't ask to make the choices too difficult for others to make, the choices that lie heavy on the conscience. Because of their situations, good people died. Harry saw the Weasley family lose their son, he lost Sirius, and he felt responsible for the deaths of Cedric, Moody, Remus, and Tonks, as well as countless others.
All incarnations of The Doctor have met wonderful, brilliant people who died in their efforts to help them, even if only knowing The Doctor for minutes. Both Harry and The Doctor were made to live with turmoil, and every choice made to survive each battle and save the day broke them.
Tragic Backstory
Lily and James Potter were murdered by Voldemort in his attempt to prevent the prophecy from coming true. Of course, as everyone knows, he failed, and he left Harry Potter an orphan. This led to Harry living with his aunt Petunia, uncle Vernon, and cousin Dudley, some of the most unpleasant muggles to grace Little Whinging. Harry was neglected and treated poorly, never treated as a beloved son as Dumbledore had hoped the Dursley family would treat him.
The Doctor lost her family, and up until recently her entire planet, to The Time War. She is a lonely traveler, the Time Lord without a home, someone who will never be able to spend eternity with the people she loves.
Smart & Loyal Companions
Harry met Ron and Hermione in his first year at Hogwarts, and the three of them have been friends ever since. They became The Golden Trio, each with their talents and temperaments serving the whole. Harry met many people throughout his years and many fought alongside him against The Dark Arts.
And just like Harry, every Doctor had companions; smart, loyal, witty, comforting companions. Every companion helped in a different way, each personality complimenting The Doctor they traveled with.
Witches, Werewolves & Ghosts
In worlds of fiction, the classic monsters are always bound to appear in their recognizable forms, if not for some creative changes. In Harry Potter, witches are bright, powerful, and not at all hideous Halloween decorations. The readers and audience are introduced to werewolves in Harry Potter And The Prisoner Of Azkaban, through both the text studied in Defence Against The Dark Arts, and Professor Lupin.
Ghosts make casual appearances in Hogwarts, and other astral forms are shown with The Resurrection Stone and the spell Priori Incantatem. In Doctor Who, an alien race called The Carrionites are close to the stereotypical witch, a werewolf makes an appearance and is linked to the royal bloodline, and ghosts find a similar counterpart in The Gelth.
A Dedicated Fan Base
There is no denying that both of these fandoms have huge fan communities. Each being entirely magical, full of adventures, heartbreak, humor, and incredibly real characters.
Both Harry Potter and Doctor Who have fans of all ages who embrace the nerdy, and either love casually or love seriously, going to all the conventions they can. Both Harry Potter and Doctor Who have people who have heard of them but have not taken the plunge into their great big wonderful worlds.
Both British
This might be obvious, but it's worth mentioning. They're both British. Harry Potter was written by J.K. Rowling, a British author, and the storyline is set in England. Doctor Who began in 1963 and although The Doctor claims to travel all of space and time, it always comes back to its British roots.
The accents, tea, and scenery scream British in both franchises. In the season 3 Doctor Who episode "The Shakespeare Code," The Doctor and Martha use the word expelliarmus when facing some witches (Carrionites), linking them both and acknowledging Harry Potter's existence.
Bigger On The Inside Technology
Harry Potter is magical, and with magic, many things are possible, including making things bigger on the inside. In Harry Potter And The Goblet Of Fire, Harry is amazed by the tent they camp in during The Quidditch World Cup. Mr. Weasley borrowed the charmed tent from his friend. It is also the same tent Harry, Ron, and Hermione use during Harry Potter And The Deathly Hallows. In the same film/novel, Hermione charms her small beaded bag to be bigger on the inside.
In Doctor Who, bigger on the inside technology is Time Lord technology. The Doctor's coat pockets are bigger on the inside, The TARDIS is bigger on the inside, the confession dial is bigger on the inside, and The Dalek prison is bigger on the inside.
Magical Ways To Time & Space Travel
The Wizarding World is full of magical ways to travel. Throughout the books and films, audiences were introduced to Floo Powder, The Ford Anglia, apparating, Time-Turners, phone booths, and broomsticks. Each associated with their varying levels of comfort and risk.
In Doctor Who, The Doctor travels in a telephone box called the TARDIS, which stands for Time And Relative Dimension In Space. It can travel in time and space. On several occasions, teleportation devices called time vortex manipulators have been used.
A Returning Enemy
Despite the efforts of both protagonists, their enemy is persistent. The Wizarding World has been afraid of Voldemort since before Harry was born, and after several quiet years, he returned. Voldemort continued to make appearances until he finally existed in the flesh in Harry Potter And The Goblet Of Fire.
It was only in The Battle Of Hogwarts, in Harry Potter And The Deathly Hallows, that Harry finally defeated him by destroying all of the Horcruxes. In Doctor Who, the bane of The Doctor's existence is The Daleks. It doesn't matter how many times The Doctor believes she has conquered them, they return stronger and smarter than before.
Actors
Because Harry Potter and Doctor Who are both British, they have many actors in common. David Tennant made an appearance in Harry Potter And The Goblet Of Fire, as Bartemius Crouch Junior. He is also notable for his role as the Tenth incarnation of The Doctor. Actor Michael Gambon, known in Harry Potter for his role as Dumbledore from the third film onwards, also appears in a Doctor Who Christmas special "A Christmas Carol," as Kazran.
Other actors that they share include Shirley Henderson (Moaning Myrtle & Ursula), John Hurt (Ollivander & War Doctor), Roger Lloyd Pack (Barty Crouch & Lumic), Bill Nighy (Scrimgeour & Dr. Black), Toby Jones (Dobby & Dream Lord), Mark Williams (Mr. Weasley & Rory's father), David Bradley (Filch & First Doctor in Twice Upon A Time), Helen McCrory (Narcissa & Calvierri) and Zoë Wanamaker (Madam Hooch & Lady Cassandra).