There is a Breton/French macaronic song which includes a bilingual pun. It came up when I asked about its tune on the ABC list. Turns out the tune is a nameless "an dro", used for a broadside ballad from 1871 which was recorded (1980s?) by the Breton group Tri Yann. It's about Breton soldiers being used as cannon fodder for the French at the time of the Franco-Prussian War and the Paris Commune. I have the full story and lyrics at home, but I'm 3000 miles away at the moment - maybe anyone who's still interested could email me directly (jack dot campin at gmail dot youknowwhat)and I'll fish it out.