Question: Heidi's Song is a 1982 American animated musical feature film whose voice cast included an American singer who at the age of three began his career in what?
Sentence (from "Heidi's Song"): It is one of only four movies Hanna-Barbera ever made that did not feature their trademark characters (along with "Charlotte's Web", "C.H.O.M.P.S.", and "Once Upon a Forest").
Relevant evidence: No