Sherlock Holmes’s flatmate and blogger seems harmless enough when you first meet him, but don’t let the frumpy exterior and questionable taste in sweaters fool you. Underneath the plaid and knits is a sharp-eyed ex-soldier and adrenaline junkie who loves the chase almost as much as his partner-in-crime-solving does.

The endearing, cowardly Nardole (Matt Lucas) was a brief companion of the 12th Doctor on the BBC TV series Doctor Who. Originally an employee of the Doctor’s wife, River Song, Nardole lost his head in an attempt to discover River’s whereabouts but was reassembled by the Doctor. The two joined forces for a short while, and then Nardole made a courageous decision that lead him down a different path. Nardole dresses in a distinctive, goofy outfit of burnt orange coat, beanie and glasses.

The wife of the Doctor and daughter of Amy Pond and Rory Williams, River Song (Alex Kingston) has an illustrious parentage on the BBC series Doctor Who. She first appears as the wife of the 11th Doctor, but because of her warped time line and supernatural abilities due to TARDIS DNA within her she makes multiple appearances across seasons. Professionally she is a Professor of Archaeology, but most of the time she is either seeking out the Doctor or being forced to harm him by his enemies. To capture her image, go for a long tunic with black leggings, wild hair and an infectiously cheerful personality.

Detective Chief Inspector John Luther (Idris Elba) works for the Serious and Serial Crime Unit on the BBC show Luther. He’s a brilliant, gritty detective who often toes the line between following the law and breaking it. Either way, tweed’s never looked better than it does on him.

Time agent, conman, companion – Jack Harkness has been all of that and more over the course of his long, strange life. If he’s not off adventuring with the Doctor, this omnisexual, immortal flirt can be found running the Torchwood Institute on Earth, defending the planet when the Doctor can’t.

After first meeting the Doctor when she was seven, Amy Pond (Karen Gillan) thought for years he was an imaginary friend. Until he showed up again the day before her wedding and it turned out her Raggedy Doctor was really an alien Time Lord (tangentially, what is up with the Doctor and redheads’ weddings?).