A cardigan was a item of clothing found on Earth. [source needed]
Worn by the Doctor
The Fifteenth Doctor wore striped cardigans. The first one he wore was in rust orange, tangerine, sapphire blue, and mauve purple. (PROSE: "Heroes of Time" [+]Part of Whotopia: The Ultimate Guide to the Whoniverse, Loading...{"namedpart":"Heroes of Time","1":"Whotopia: The Ultimate Guide to the Whoniverse (reference book)"}; TV: The Church on Ruby Road) He switched for a mint green cardigan with a beige trim and stripes done in mustard yellow, scarlet, and raven black. (TV: The Church on Ruby Road)
The Fourth Doctor wore a dark brown cardigan with diamonds when he met the K1 Robot, (TV: Robot) when he faced Wirrn, (TV: The Ark in Space) when he fought Field Major Styre of the Sontaran G3 Military Assessment Survey and tricked his marshal into cancelling an invasion of Earth, (TV: The Sontaran Experiment) when he first met Davros who forged the first Daleks during the Genesis Incident, (TV: Genesis of the Daleks) and when he faced Nomad Cybermen during their gambit to destroy Voga after the Great Cyber War. (TV: Revenge of the Cybermen)
The Twelfth Doctor wore a navy blue cardigan with a matching covert coat; (TV: Deep Breath. etc.) most notably during the Good Dalek Incident, (TV: Into the Dalek) and when he met Robin Hood. (TV: Robot of Sherwood)
The Warrior, a parallel version of the Fifth Doctor who looked as the Sixth, spent his first hours in his predecessor's cardigan before switching for double-breasted waistcoats of moleskin with double fob chains of bronze similar to the N-Space Doctor's war incarnation. (AUDIO: Dust Devil)
Worn by Companions
Barbara Wright's cardigan was unravelled by Ian Chesterton while they were in the Space Museum so they could ensure they weren't repeating their paths. (TV: "The Dimensions of Time") Barbara later wore another cardigan while on Aridius. It was later used by Ian to set a trap for the Dalek guarding the TARDIS. (TV: "The Death of Time")
Rani Chandra wore a fuchsia cardigan with a pink blouse. (TV: The Mark of the Beserker)
Martha Jones wore a black cardigan over her vermillion tank top, which she immediately removed upon arriving on the SS Pentallian due to the stifling heat on board the ship. (TV: 42) She was wearing a wine cardigan when she and the Tenth Doctor met Sally Sparrow. (TV: Blink)
Ace wore a black cardigan with her emerald t-shirt when she and the Seventh Doctor helped UNIT to fight Morgaine and the Destroyer. (TV: Battlefield)
Clara Oswald wore a black cardigan with her white blouse and tartan skirt. (TV: The Time of the Doctor, Deep Breath)
Amy Pond wore a cream cardigan when scolding Mels Zucker about stealing a bus. (TV: Let's Kill Hitler)
Angie and Artie Maitland wore cardigans; Angie's in many colours, and Artie's in midnight blue. Both did this during the Battle of Hedgewick's World of Wonders. (TV: Nightmare in Silver)
Evelyn Smythe often wore cardigans, namely an orange one (AUDIO: The Marian Conspiracy)
Donna Noble wore a mauve cardigan when she and the Tenth Doctor met River Song and some Vashta Nerada. (TV: Silence in the Library/Forest of the Dead)
Liz Shaw wore a raven black cardigan when she risked her own life to save the Third Doctor from the First Rani. (TV: Dimensions in Time)
Worn by Others
Allison Williams wore a beige cardigan when she helped the Seventh Doctor during the Hand of Omega Incident. (TV: Remembrance of the Daleks)
Ursula Blake wore a silver cardigan up to being absorbed by the Absorbaloff. (TV: Love and Monsters)
St John Colchester often wore cardigans, which he referred to as "cardies". (AUDIO: Escape Room, etc.)