Robot Yeti

The Yeti Robots were a type of robot created by the Great Intelligence to impersonate real real Yetis.

Appearance
The Yeti robots were large and hairy, which disguise the control spheres that provided its motive power.(DW: The Abominable Snowmen, The Web of Fear)

History
The Yeti were originally designed by the Great Intelligence in the guise of real Yeti, in 1935 Tibet. DW: ''The Abominable Snowmen'

More than thirty years later, dead Robot Yeti, on display, awoke and took over London.(DW: The Web of Fear)

The latter attempt was one of the events which caused the formation of the UNIT. (unit.org.uk)

Behind the Scenes
The date of the second Yeti invasion remains a point of contention for Doctor Who fans, because it brings up the UNIT dating controversy. The perhaps not entirely canonical UNIT website gives the date of the incident as 1968, the same year The Web of Fear aired.