Robot clown

The Robot Clowns were androids modelled on clowns.

Psychic Circus
Robot Clowns assisted the Chief Clown in running the Psychic Circus. They were responsible for making people perform and entertain the Gods of Ragnarok. These clowns were not destroyed by them, but were used so that they would be entertained during the time when the humans and other species went to take part in the Talent Show. They were destroyed when the Seventh Doctor blew up the circus. (TV: The Greatest Show in the Galaxy)

Elijah Spellman
Elijah Spellman also made a circus full of Robot Mannequins in the shape of Clowns. He used them to attack Sarah Jane Smith and her friends, Clyde Langer, Luke Smith and Rani Chandra. She used her sonic lipstick to stop them from attacking the group. (TV: The Day of the Clown)

Earth robots
On Earth near the mid-21st century, advances in robot technology, thanks to Alistair Gryffen and his Thought Matrix, meant that robot clowns started appearing in circuses. (TV: Robot Gladiators) Darius Pike once had a nightmare in which he was trapped in his car, surrounded by three robot clowns along with a human clown.

Two robot clowns, Chuckles and Boris, were taken to be gladiators in Crashclub. K9 Mark 2 met and befriended them when he went undercover to take down the organisation. Boris was destroyed fighting the Pain-Maker, but he was rebuilt after Crashclub was shut down, Chuckles and Boris then returned to the circus. (TV: Robot Gladiators)