Tweedle-dee

1. A fictional little fat man who is the twin brother of Tweedle-dum and appears in multiple artistic works, including certain nursery rhymes and Lewis Carroll's Through the Looking-Glass.

plural Tweedle-dees

1. One of a pair (the other of the pair being Tweedle-dum) of nominally different (often: but practically identical) things.

   "She can't tell a Tweedle-dum from a Tweedle-dee."

   1999, Katherine Paterson, The king's equal, page 13

   3 more examples

   Some ſay, compar’d to Bononcini, / That Mynheer Handel’s but a Ninny; / Others aver, that he to Handel / Is ſcarcely fit to hold a Candle: / Strange all this Difference ſhould be, / ’Twixt Tweedle-dum and Tweedle-dee!

   1773, “Epigram on the Feuds between Handel and Bononcini”, in Miscellaneous Poems, Manchester: J. Harrop, pp 343–44

   How can we get the tweedle-dums and the tweedle-dees together for united action in the interests of the masses of the people?

   1907, The Medical world, volume 25, page 216

   Suppose we have any axiom of the form: (2) For every Tweedledee there is a Tweedledum R-related to it. Axioms of the form (2) cut two ways. They can be construed as putting a limit on the Tweedledees: only those exist for which there is an R-related Tweedledum. On the other hand, they can be seen as postulating the existence of a rich collection of Tweedledums. There are so many of them that there is at least one R-related to every single Tweedledee.

   1989, Jon Barwise, The Situation in Logic, page 189