The Whomobile was a futuristic-looking vehicle designed by the Third Doctor. It was similar to a hovercraft and was capable of flight.
History
The Third Doctor first used the Whomobile to search for the secret base of Operation Golden Age. (TV: Invasion of the Dinosaurs) It was later used by (and then used to chase after) Lupton when he stole the Doctor's Metebelis Crystal. (TV: Planet of the Spiders)
Behind the scenes
The name
The vehicle was not created for Doctor Who, but was personally commissioned by Jon Pertwee, who retained possession of it after his stint as the Doctor. Pertwee gave it the name "Whomobile" during press interviews, but it was also known — again, off-screen — as "Alien". Had the vehicle been named in Doctor Who, it almost certainly would not have been called "the Whomobile", as this violated producer Barry Letts' strong conviction against making plays on the programme's title. The Doctor Who Technical Manual referred to it simply as "the Doctor's Car."
The name was spoken in an audio drama featuring Pertwee and Elisabeth Sladen recorded for Glorious Goodwood. It was never released until it appeared on one of the Doctor Who at the BBC CDs in the mid-2000s.
As a real-life vehicle
The Whomobile (reg: WVO 2M) was one of Jon Pertwee's personal vehicles. He retained possession of it until nearly the end of his life.
The Whomobile was hastily written into the script of Invasion of the Dinosaurs, where it replaced an army motorcycle as the Doctor's transport around the deserted London. The Whomobile's roof/door section had not been completed at the time of filming, so a motor-boat windscreen was fitted to make the car legally roadworthy. The vehicle was classified technically as an "Invalid Tricycle".
When Pertwee demonstrated the vehicle to Peter Purves on the Monday 7 January 1974 edition of Blue Peter during his tenure, he revealed that the vehicle was roadworthy and legal, though he mentioned that the BBC forbade him or any of the crew from removing it from the studios except for outside shoots. It was capable of a top speed of 105 mph (roughly 169 kph).
As documentary subject
Pertwee presented the Whomobile in the documentary Thirty Years in the TARDIS.
Other appearances
Jon Pertwee, in costume and in character as the Doctor, appeared with the Whomobile in Billy Smart's Children's Circus on the afternoon of Sunday 4 November 1973 (broadcast Sunday 6 January 1974). The Doctor Who theme music played as the Doctor drove the vehicle into the circus ring, with Gabriella Smart, sister of young ringmaster David Smart Jr., in the passenger seat. The Doctor then chatted briefly with David, before driving off with Gabriella to help find her lost performing dogs.