In 1954, the CBC (Canadian Broadcasting Company) got the rights to create their own version of Howdy Doody, with their own characters and copies of the original puppets. The original emcee, a faux-Mountie named Timber Tom, was played James Doohan (Scotty from Star Trek), and an occasional guest host was Ranger Bob, played by one William Shatner. The Canadian Howdy Doody also featured the TV debut of Robert Goulet as Trapper Pierre.
Among the puppet characters was a "Mr. X," voiced by Claude Rae, who zipped through time and space in a machine called a "Whatsis Box," teaching children about history. Mr X's tenure on the program was short-lived when numerous parents complained that he was too scary.
The CBC's Supervisor of Drama Production at the time was one Sydney Newman, who would later move to England to head the Drama departments of ABC-TV and eventually the BBC, where he very likely had Mr X and his Whatsis Box in mind when he formulated the concept of Doctor Who.
from the IMDB entry on James Doohan:
"James Doohan was originally cast as Timber Tom but wanted more money than the CBC was prepared to pay and so was replaced by Mews, who couldn't appear for the first week of the show and was temporarily replaced as host by William Shatner as Ranger Bob."