Tweedledum and Tweedledee

 
Pronunciation: /twiːd(ə)lˈdʌm, twiːd(ə)lˈdiː/

noun

  • a pair of people or things that are virtually indistinguishable: the umpires conferred, like Tweedledum and Tweedledee in their striped shirts

Origin:

originally names applied to the composers Bononcini (1670–1747) and Handel, in a 1725 satire by John Byrom (1692–1763); they were later used for two identical characters in Lewis Carroll's Through the Looking Glass