When YTV launched, it had a block of programs for preschoolers with a focus on Canadian content.
In 1991, YTV began airing host segments during the block featuring their PJs (Program Jockeys) and the Grogs (replaced by The Fuzzpaws in 1994).
In 1994[citation needed], YTV's preschool block received the name The Treehouse.
The Treehouse host segments were replaced with short series (some produced by YTV in-house) and promos.
The Fuzzpaws got their own short series on YTV Jr., and PJ Katie became Jenny on The Zone.