Russell T Davis had a specific purpose for Adam, who appeared in Dalek and The Long Game, to do a story about a failed companion. Adam was just that, as his selfish actions in The Long Game, in which he bio-hacked some future tech into his head, went against the Doctor’s rules about time travel. It didn’t help that adam was already so unlikeable and dull before he crossed that line.
The “comic relief” in Peter Capaldi’s last season, Nardole was anything but. Played by Matt Lucas, Nardloe was an android that first appeared in The Husbands of River Song. Instead of playing off of the great chemistry between the Doctor and Bill, Nardole mostly brought each episode to a standstill as a decidedly unfunny exposition machine.
3. Vastra, Jenny, and Strax
After the deaths of Rory and Amy, Vastra, Jenny, and Strax took care of the Doctor as he grieved in Victorian London. Investigators of the bizarre in their own right, The reformed Sontarion, the Siluran, and her wife were a welcome addition to the show, and there was even talk of a spin-off. Alas, by Deep Breath they had become a little stale, and Steven Moffat never revisited them.
4. Jackie and Mickey
These two are a little different as they were more of a foil to Rose than the Doctor. Still, Mickey and Jackie became defenders of the Earth (in two dimensions) in their own right, outgrowing their original characterisation and becoming vital to many of the Doctor and Rose’s adventures.
The Last Centurion was given a bit of a raw deal. Not by Amy, or the Doctor, but by Steven Moffat himself as he kept Rory in a cycle of romantic anguish as the showrunner recycled the same relationship drama between Mr and Mrs Pond over and over again. She married you Rory, stop being so weird.
6. Captain Jack
Former Timer Agent and sometime immortal hero, Captain Jack was one of the most progressive characters on British teatime television. After adventuring with the 9th Doctor and Rose, Jack went on to his own spin-off show Torchwood. Torchwood is the best place for Jack as he’s given a deeper character arc, as he often hams it up in the vicinity of the Doctor. That said, many fans would welcome a return.
The Impossible Girl quickly became the most important character in the show’s history thanks to Steven Moffat’s often annoying tendancy of macking Clara responsible for too much of the Doctor’s history. Jenna Coleman was fine in the role, but Clara seemed to switch personalites in each of her three seasons in the Tardis, and most of her storylines were never properly resolved. How can Orson Pink be alive if Danny died? That’s just one.
The Girl Who Waited, Amy Pond was the first face the 11th Doctor’s huge face ever saw. While Amy’s relationship with Rory was a little hit and miss quality-wise (except for the episode The Girl Who Waited) it was Amy’s fairy tale relationship with the Doctor that brought out the best in her.
Poor Martha, poor underrated Martha. Following Rose was never going to be an easy task, but Martha Jones was certainly up to it. Despite having an unrequited crush on the Doctor, who doesn’t, Martha was frequently part of the best episodes of new Who, with her finest hour (or two) coming in the Human Nature/Family of Blood two-parter.
The 12th Doctor’s best companion, Bill was funny, charming, and brilliantly logical. Pearl Mackie’s chemistry with Peter Capaldi was often the saving grace to a lot of medicore episodes in the show’s tenth season. It’s a same that her time in the Tardis was David Tennent era short.
A full season of Catherine Tate shouldn’t have worked, but it did like gangbusters. After Rose and Martha, Donna was a refreshing change of pace for the 10th Doctor as he got to travel through time and spac with his best mate. Season four of the show isn’t the best of the 10th Doctor’s run, but Tate and Tennent are having so much fun that it’s easy to ignore some of the weaker stories. Except the daughter, that was just weird.
The first companion of new Who casts a long shadow. Rose was a perfect Doctor Who companion because she was down to earth, relatable, and crucially, didn’t need to be the most important woman in the universe. She was the 9th Doctor’s hearts when his was broken after the Time War, and his saviour when he was more Scottish, and a little bit foxy. Although Rose ending up with a human copy of the Doctor was prime T Davis strangeness.