The dual role of identical cousins or siblings, with contrasting personalities (Carlos Ramirez / Luis Ramirez), was a common plot device and special effects' technique (using split-screen) in 1960's sitcoms. It was used for cousins Samantha Stephens / Serena in Bewitched (1964), Herman / Charlie Munster in Knock Wood, Here Comes Charlie (1964) and Jeannie / evil fraternal twin sister (also named Jeannie) in I Dream of Jeannie (1965).