Enantiomorphs

"They were standing under a tree, each with an arm around the other's neck, and Alice knew which was which in a moment, because one of them had 'DUM' embroidered on his collar, and the other had 'DEE'.  'I suppose they've each got 'TWEEDLE' around at the back of the collar' she said to herself.

They stood so still that she quite forgot they were alive, and she was just looking round to see if the word 'TWEEDLE' was written at the back of each collar, when she was startled by a voice coming from the one marked 'DUM'.

'If you think we're waxworks,' he said, 'you ought to pay, you know.  Waxworks weren't made to be looked at for nothing. Nohow!'

'Contrariwise,' added the one marked 'DEE', 'if you think we're alive, you ought to speak.' "

Through the Looking-Glass and what Alice found there  Lewis Carroll

[after the epigram by John Byrom, on the rivalry between Handel and Giovanni Battista Bononcini]:-

"Some say compared 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!"