"What Hollywood actor appeared as a child in Elvis Presley's film ""It Happened at the World's Fair"" in 1963, was nominated for an Emmy Award for Outstanding Lead Actor in a Limited Series or a Special for the TV film ""Elvis"" (1979), provided Elvis's voice for a scene in ""Forrest Gump"" (1994) and was an Elvis impersonator in ""3000 Miles to Graceland"" (2001)?"