Elephant

An elephant was a type of proboscidean related to the mammoth. It was found on the planet Earth.

Encounters with elephants
The Doctor and his companions occasionally encountered elephants.

Among the prizes the First Doctor won in a game of backgammon against Kublai Khan in the 13th century were thirty-five elephants with ceremonial bridles. (DW: Marco Polo)

Elephants were one of the animal species brought on board the Ark to escape the destruction of Earth. Dodo Chaplet pointed an Indian elephant out to the First Doctor and Steven Taylor and they proceeded to pet it. (DW: The Ark)

The Second Doctor and Jamie McCrimmon once used a herd of animals – which included s – to stampede a group of Quarks. (TVC: Jungle of Doom)

The Seventh Doctor and Ace saw elephants living in the Ngorogoro Crater in 1926. (DWM: Prelude: Birthright)

In about 120 AD, the Tenth Doctor learned that Roman authorities kept elephants as a part of a menagerie that included leopards, giraffes and a wide range of other, chiefly African animals. Some of the beasts were kept for hunting, and others were used to face off against prisoners in local arenas. The Doctor was incensed by the practise, because he knew it would lead to the extinction of several of the species. (NSA: The Stone Rose)

Whilst in India in 1947, the Doctor and Donna Noble travelled wtih Gandhi and his party by elephant. Donna was amused by the rolling motion caused by the elephant's gait. Consequently, both she and the Doctor had a hard time controlling their laughter. As was customary in India, these "transport elephants" were highly decorated with flowers, bells, and a howdah. (NSA: Ghosts of India)

Cultural references to elephants
In Voyager's dream world, a waterfall existed that was bordered by two elephant statues. (DWM: Voyager)

When talking to Davros about logic, the Fourth Doctor says "All elephants are pink, Nellie is an elephant, therefore, Nellie is pink!". When he asks if it logical and Davros agrees, the Doctor and Tyssan corrects him that elephants aren't pink. DW: Destiny of the Daleks

Human folklore stated that elephants never forget anything. It was a running gag between the Sixth Doctor and his companion Melanie Bush that she had the memory of an elephant. (DW: The Ultimate Foe, BFA: The One Doctor, DW: Time and the Rani, BFA: Unregenerate!)