I have a Dutch one: we have the expression “a law of Medes and Persians”, which denotes a law that cannot be broken (after the ). In Dutch it is een wet van Meden en Perzen. As a child, a friend of mine thought it was een wet van meten en persen, which sounds the same but means “a law of measuring and squeezing”.

Huh?! That’s a new one on me – I use them interchangeably depending on how the words flow and avoiding repetitions of “that”. A quick web search turned up http://www.grammarbook.com/grammar/whoVwhVt.asp, and I presume (not “assume” *g*) you’re referring to Rule 2. But for me no more than the comma is required to distinguish a supplementary clause from a qualifying clause. I guess it must be another of those US/Brit tomarto/tomayto things!

On the subject of word play, I have a book somewhere with a couple of dozen Latin-English homonyms, such as “Caesar adsum iam forte. Pompey ad erat” (”Caesar had some jam for tea; Pompey had a rat”).