Kevin (When Worlds Collide)

Kevin was a robotic Tyrannosaurus rex who was briefly a companion of the Eleventh Doctor, and a co-companion of Amy Pond and Rory Williams. A robot "actor" from an amusement park planet who found pretending to be a T-Rex unsettling, Kevin asked to travel with the Doctor so that he could find a better place for himself. The Doctor somehow managed to get Kevin into the TARDIS and he travelled as a member of the TARDIS crew for an unspecified number of adventures.

Kevin's size and appearance occasionally caused difficulty during his travels with the Doctor. He almost caused a panic in Japan when the locals mistook him for a kaiju (a colossal monster in the vein of the famous "Godzilla") and thought he was going to destroy Tokyo. When the TARDIS visited a space station known for its Granberry Smoothies, Kevin elected to remain inside the TARDIS, but eventually came to the rescue when his friends were threatened by possessed cultists.

When a mind-controlling space squid arrived outside the station, Kevin and the Doctor were the only two individuals aboard that were immune to its powers. After rescuing Amy and Rory from the cultists, the Doctor fashioned a battle suit for Kevin and gave the robotic T-Rex a concoction that was designed to knock the cephalopod out. Kevin engaged the squid in combat and, making good use of the extended mechanical arms on his battle suit, he defeated the squid and freed the population of the station. Kevin decided to remain on the station as its new chief of security.

Personality
Kevin was generally mild-mannered and polite. He did not enjoy portraying a T-Rex, describing the experience as wanting to kill people but not knowing why, and not being able to stop himself. The robot T-Rex was also a capable fighter despite his friendly disposition. He allowed Rory to use him as a mount in combat, and carried the Doctor to safety when they were being pursued by the cultists.

Behind the scenes

 * Kevin is never shown entering or exiting the TARDIS, although he did stick his head outside the door in order to converse with the Doctor.
 * Three of the crew of the space station where Kevin is eventually employed are named "Fillion", "Katic", and "Quinn", after Nathan Fillion, Stana Katic, and Molly Quinn, the principle actors in the American television series "Castle".