<Tr> <Td> "String Module Error: Match not found" (1976) </Td> <Td> "Happy Days" (1976) </Td> <Td> "Devil with a Blue Dress On" (1976) </Td> </Tr> <Tr> <Td_colspan="2"> <Table> <Tr> <Td> "Whachersign" (1976) </Td> <Td> "Happy Days" (1976) </Td> <Td> "Devil with a Blue Dress On" (1976) </Td> </Tr> </Table> </Td> </Tr> <Table> <Tr> <Td> "Whachersign" (1976) </Td> <Td> "Happy Days" (1976) </Td> <Td> "Devil with a Blue Dress On" (1976) </Td> </Tr> </Table> <Tr> <Td> "Whachersign" (1976) </Td> <Td> "Happy Days" (1976) </Td> <Td> "Devil with a Blue Dress On" (1976) </Td> </Tr>

Who sang the theme tune to happy days