The title is based on the title of the 1925 song, "Clap Hands! Here Comes Charlie!" by Billy Rose, Ballard MacDonald and Joseph Meyer.
The dual role of identical cousins or siblings, with contrasting personalities (Herman / Charlie Munster), 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), Carlos Ramirez / Luis Ramirez in The Convent Gets the Business (1969) and Jeannie / evil fraternal twin sister (also named Jeannie) in I Dream of Jeannie (1965).
USD 5,000.00, in 1964, would be equivalent to USD 40,715.97 in 2018, if adjusted for US Inflation.
The "split-screen" effect for two people with differing personalities was also used on the sitcom "The Patty Duke Show" (1963). Patty Duke plays both Patty Lane, a normal, chatty, rambunctious teenager and her "identical cousin," Cathy Lane, who is sophisticated, brainy and demure.