K-9 and Sarah Jane Smith Doctor Who costume on display...

After 50 years every Doctor Who fan has their own favorites, whether it be the Time Lord himself through his various regenerations, favourite monsters from his eclectic pantheon of aliens and enemies, or his traveling Companions in the TARDIS.

Doctor Who Companions K-9 and Sarah Jane Smith costume exhibit

Here's the costume worn by one of his longest serving Companions, 'Sarah Jane Smith' played by Elisabeth Sladen and his faithful robotic dog, K-9, on display at the Doctor Who Experience in Cardiff Bay, Wales on May 20, 2013.

Sarah Jane Smith costume worn by Elisabeth Sladen in Doctor Who

Fan-favourite Sarah Jane Smith traveled with the Third (Jon Pertwee) and Fourth (Tom Baker) incarnations of the Doctor from 1973 to 1976, starred in a pilot for a proposed Doctor Who spin-off called 'K-9 and Company' in 1981, plus returned to meet the Tenth Doctor (David Tennant) in the Doctor Who revival episode in 2006, 'School Reunion' (in which she wore this outfit).

Due to her popularity she even received her own spin-off series in 2007, The Sarah Jane Adventures, which ran for five seasons, until the untimely death of Elisabeth Sladen in April 2011.

If you're a fan of Doctor Who's Companions, be sure to also check out these Amy Pond and Rory Williams costumes from Doctor Who on display.

K-9 replica on display at the Doctor Who Experience

K-9 was a classic Companion of the Fourth Doctor, who acquired the 51st century super computer in the form of a dog from 'Professor Marius' in 1977's The Invisible Enemy. In addition to his computational prowess he also has defensive systems including a laser in his nose.

When I was growing up watching the kids sci-fi TV show I always wanted my own loyal K-9, with his trademark catchphrase "Affirmative!", as he seemed so futuristic and technologically advanced at the time.

From one famous metal dog to some of the Doctor's more formidable foes, if you like K-9 be sure to take a look at these generations of the cyborg Daleks and Cybermen costumes and props on display.

Own your own K-9 merchandise: Doctor Who K-9 Bobble Head

Doctor Who K-9 Diecast Keychain