Pizza Forest is a fictional chain of children's-themed pizza restaurants that features singing animals. The singing is very bad.
Daria Morgendorffer and her family visit the Lawndale location in the episode, "Esteemsters." The chain is established as somewhere Daria and Quinn used to be taken as children; apparently, nobody enjoyed it as an older Quinn is horrified at the idea of going back there and Daria specifically thinks of it as a way to make her family suffer. Daria pretends she really misses the place and it'd make her happy in order to force her parents to go there.
On the old Daria website, Jane Lane gave the restaurant a 2.0 out of 10, noting that the costumed actors do not respond when stricken and the pizza itself "tastes like frozen supermarket kind, only worse".