Original: They were created by Dr. Kit Pedler (the unofficial scientific advisor to the programme) and Gerry Davis in 1966, first appearing in the serial, The Tenth Planet, the last to feature William Hartnell as the First Doctor.
Simplified: They were created by Dr. Kit Pedler (the unofficial scientific advisor to the programme) and Gerry Davis in 1966, first appearing in the serial, The Tenth Planet, which was the last to feature William Hartnell as the First Doctor.