https://en.wikipedia.org/wiki/Polka_Dot_Door
Polka Dot Door is a Canadian children's television series which was produced by the Ontario Education Communications Authority (later known as TVOntario) from 1971 to 1993. The series features two hosts who acknowledge and present the show directly to the home viewing audience.
The content of the shows was generally geared towards education and creativity. Each week of episodes focused on a single theme with each weekday assigned a different "motif" in which the theme was explored in different ways (For example, Tuesdays were "Dress-Up Day" in which the hosts would use costumes to explore the theme).
One of the most well-known elements of the series was "Polkaroo": a mythical character whose name combines the words "polka dot" and "kangaroo". Normally played by the male host in costume, Polkaroo would appear to the female host to perform a pantomime; upon the second host's return, they would typically express disappointment when informed that they had once again missed Polkaroo. In earlier years, Polkaroo appeared just once per week on "Imagination Day", although due to the character's popularity additional appearances were added later in the show's run.
Another feature of the show was "looking through the polka-dot-door." This feature of the show, usually on "Finding-Out Day," was unique in that the camera would zoom in to a special dot on the door, which would open up to reveal a short educational film.