I am familiar with THAT! Last year I had to translate a poem called The Last Pastoral. It had a futuristic setting and one of the devices of the poem was a broken audio player that spouted fragments of English pastoral poetry. I had to reconstruct enough of each original poem to plausibly insert its fragments, and play with style to try to make a never-before-seen phrase sound like a familiar one. I considered using original poetry in the target language instead, but the pastoral was important to the theme, so I kept it.

Thanks (somewhat belatedly) for the link!

My father read an Italian novel with some dialogue in Sicilian, and was curious to see how the difference was rendered in an English translation (which his wife was reading). It was ignored. I suggested that Sicilian could be rendered as Scots, but somehow he did not find that solution satisfactory.

It's very hard to know what to do about dialects. A classic problem is the Spartans in Lysistrata; I've seen their dialect done both as Scots and American Southern, both of which make sense theoretically but seem kind of silly in practice.

Speaking of Scots and Aristophanes, The Puddocks.