I don't know if you watch Teletubbies either, Hyke, but the idea is this: The show cuts away from the presenters in the studio to a short documentary-style film about a topic or theme of interest. For example, the producers might insert a short film depicting a school crossing guard interacting with people crossing the road near the school; or showing how cows get milked, or how crayons are manufactured; or perhaps showing two children caring for their pet rabbits, or giving their dog a bath. The transition from studio to documentary film is achieved, in the case of the Teletubbies, when the antenna of one of them lights up and the film begins to appear on the little screen on its tummy. On Play School, the transitional device is to choose a random window, with the film first appearing into view through that window. On Play School there were traditionally three different shapes of windows in which the film might appear; now there are four.