Why ドルフィン, ドルファン and ドルフォン?

Question

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 ほらドルファン

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?

Answer 1

This is a wordplay analogous to "holy moly" or "see you later alligator". It's completely nonsense except that it sounds somewhat rhythmical and humorous. See 地口 for similar examples. (Note that rhyming in its narrow sense is less important in Japanese.)

(EDIT: Or maybe you can think of this as a "prologue to the scat part" since scat consists of meaningless vocals.)

To be clear, ドルファン and ドルフォン are not "different ways to write dolphin". This English word is always written as ドルフィン in katakana.