Crossword clue: butters stotch, pip pirrup, and wendy testaburger are all characters in which long running animated tv series

The most common answer is park (4 letters).

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

Possible answers

park 4 letters otdb

a large area of land preserved in its natural state as public property

south 5 letters otdb

the region of the United States lying to the south of the Mason-Dixon line