In a third season episode of 'Kingdom', Terry was upset because Geraldine Merrick was going to destroy the crop circles that had mysteriously... um... cropped up in her wheat field outside of Market Shipborough. But his lawyer, Peter Kingdom, said that it would be impossible to stop her. After all, it was her land.
Not that Terry was deterred. As he told his son, "Would that stop the Doctor?"
If it had been left at that, we might have been able to dismiss his comment as being about the general practitioner for that area of Norfolk. But because of later circumstances, we have to accept that he was referring to the Gallifreyan Time Lord who is known only as "The Doctor".
NOT as "Doctor Who" - that's the name of the TV show that was created with the backing of UNIT to cover up the activities of the Doctor in real life. Like the dismissal of UFO sightings as being weather balloons or swamp gas, complaints made about the Doctor could be shrugged off as a vivid imagination combined with the TV show and a few pints. (This project began with several movies starring Peter Cushing as a character actually named "Doctor Who".)
Back when the Doctor still looked like a gangly Mancunian in a jumpsuit, back in his ninth incarnation, he gave Mickey Smith a computer disk containing a program that would wipe out all mention of the Doctor from internet and computer memory storage units all over the world. But it's apparent that Mickey never bothered to put the program into action; or at best it didn't matter in the end, because there was no way to erase him from the memories of those people who already knew of him.
There would be thousands of people who would have remembered the Cybermen invasion of London, others in outlying villages across the country who remembered when the Doctor came to the rescue when their hamlets were attacked by Daemons or Axions.
Since Terry was such a fanatic about such alien invasions - he surely would have remembered when the Visitors nearly took over the world in the early 1980's, as well as when the giant Canamids dropped by for lunch - he would have learned about the Doctor long before that computer program had a chance to spread its virus. So Toobworld Central accepts that he was referring to the Doctor. As for those circumstances that occurred later in the episode, Peter Kingdom and Ms. Merrick, along with Detective Constable Yelland, had a close encounter with a man wandering through those wheat-fields dressed as the fourth incarnation of the Doctor, complete with fifteen foot long scarf and a packet of jelly babies. It was the first sign of a different sort of invasion - that of the UFO enthusiasts (many of whom would later travel to Calfiornia for another fruitless gathering, as seen on 'Monk'). Among those fanatics, somebody used the Orkan catch-phrase "Nanu, Nanu," which we refuse to accept as a Zonk - that is, as a discrepancy. "Nanu Nanu" probably became known and absorbed into the English language after the existence of Mork was made known to the general public. Having a child by an Earth-woman, a boy named Mearth who would be publicly aging backwards, probably put the kibosh on Mork's hope to remain anonymous.
As with all such revelations in Toobworld, like the eventual one for 'The Munsters' family or for the Melmacian who was code-named 'ALF", there must have been the inevitabe sensation in the media about it (although unseen by the Trueniverse audience). Eventually however, the novelty passed and for the most part that guy from Ork, 'Mork & Mindy', his Terran wife, faded from people's memories, in much the same way as happened with the Eugenics Wars of the late 1990's.
As Terry would come to say during the episode, "In an infinite universe, anything is possible."