At the end-of-course ceilidh at Sabhal Mòr Ostaig, one of the Irish guys read a story which was half in English and half in Irish. It was very funny, if you understood both languages; those who didn’t missed quite a lot. Even speakers of Scottish Gaelic found it quite difficult to understand all the Irish bits, which suggests to me that Irish and Scottish Gaelic aren’t as mutually comprehensible as some claim.

This type of story is called macaronic, a word coined in the 16th century by Teofilo Folengo, an Italian poet, to refer to a type of verse he invented in which he mixed Italian and Latin for comic effect. He based the name on macaroni, which he described in Latin as pulmentum farina, caseo, botiro compaginatum, grossum, rude, et rusticanum (a savoury dish bound together with flour, cheese [and] butter, [a dish] which is fat, coarse, and rustic).

The word was first used in English the following century and was used to refer to any type of verse which mixes two or more languages together.

Source: http://www.worldwidewords.org/weirdwords/ww-wei1.htm.

Here are links to a few examples of Macaronic songs in English and Irish:
http://academic.evergreen.edu/w/williams/macaronic.htm