Walden Robert Cassotto ( May 14 , 1936 â `` December 20 , 1973 ) , better known as Bobby Darin , was an American pop singer , most famous during the 1950s . Bobby Darin ( May 14 , 1936 â `` December 20 , 1973 ) , born Walden Robert Perciville Cassotto , was an American singer , actor and accomplished musician .