Scarecrow

Scarecrows were man-like figures intended to deter crows from eating crops.

Scarecrow disguises
briefly dressed himself up as one in order to spy on the Sixth Doctor. (TV: The Mark of the Rani)

After his defeat by the Tenth Doctor, Son of Mine was turned immortal, and left forever aware of his fate, but immobile, and was dressed up as one of his animated scarecrows tasked with guarding England's fields. (TV: The Family of Blood)

Animated scarecrows
The Time Lords made animated scarecrows in a plot to draw out the Second Doctor and enforce his regeneration and exile. (COMIC: The Night Walkers) The Family of Blood also made animated scarecrows as their henchmen. (TV: Human Nature / The Family of Blood)

Behind the scenes

 * The script to the un-produced film Doctor Who Meets Scratchman also featured walking scarecrows.
 * Scarecrow from the television stories Human Nature/The Family of Blood is one of the enemies in Doctor Who Legacy mobile game.