Crocodiles were a species of reptile.
In ancient Egypt, Thoueris controlled the crocodiles in the River Nile with her ring. The Eighth Doctor took her ring and used it to turn the crocodiles against her. (COMIC: The Power of Thoueris!) According to the Twelfth Doctor, the people of Crocodilopolis in ancient Egypt worshipped a giant crocodile, which the Doctor claimed was a "useful coincidence". (TV: The Caretaker)
According to the Legend of Sutekh, they were among the animals associated with the titular Osiran god of evil and violence, Sutekh. Other animals associated by the Egyptian tradition with the cults of Sutekh included donkeys, hippopotamuses and pigs. (PROSE: Background)
Near the Karabar Caves, India on 31 December 1926, the Fifth Doctor and his companions Nyssa, Tegan Jovanka and Turlough were forced to cross a den of crocodiles. Tegan referred to one of them as "an overgrown handbag." (AUDIO: The Emerald Tiger)
A lake on one planet was infested with crocodiles. The first of the tests of Trefus required that one of the fair-haired people to swim across this lake. Saul completed this test when the Second Doctor used explosives to temporarily stun the crocodiles. (COMIC: The Tests of Trefus)