Pudding-brain

"Pudding-brain" was a term used to insult more primitive species, such as humans. The Doctor, in his twelfth incarnation, first used this term to describe the people of the Victorian era whilst he was investigating the death of a female Tyrannosaurus rex dinosaur that had been rampaging around London. He called Earth the "planet of the pudding-brains". (TV: Deep Breath)

He later used the phrase "pudding-headed primitive" to describe the Sheriff of Nottingham. (TV: Robot of Sherwood) He described Rigsy as a "fluorescent pudding brain," (TV: Flatline) which Rigsy later recalled. (TV: Face the Raven) When greeting a native of Dyssiopeia, the Doctor called him a "pudding-brained, mouth-flapping dunderheid". (COMIC: Planet of the Rude)

Behind the scenes
In the original script for Face the Raven, the Doctor was to refer to Rigsy as a "Florescent Pudding Brain". This line was cut from the completed episode.