Credit for the song must partially go to spiderflower. We were having a discussion about what a wedding between Robin and Chopper would be like(Zoro walks her down the aisle, but winds up in Alabasta through sheer force of horrible navigation) and spider proposed that Franky plays the guitar and sings, in place of an organist, due to their lack of a true musician. Then she came up with the first line of the song (Oh, when a reindeer loves a woman). When I needed a song for this fic, I took that line and extrapolated.