There is a song by Kingo Hamada called 街のドルフィン that frequently appears on 80's city pop compilations. It seems to be a silly song about a young boy who captures a dolphin and they swim together in the light of the milky way (roughly interpreting). At the end of each verse, Hamada sings these words:
ほらドルフィン ドルファン ドルフォン
(Which at the end of the song leads into a scat section frequently featured in internet meme videos)
My question is why does he change the vowel in the word ドルフィン to ドルファン and ドルフォン? Is he just playing around with the different ways the english word "dolphin" can be turned into Japanese with Katakana and still sound like the original word? Or is there some other joke being made here?