That, along with "Jumpin' Jack Flash", is my favorite song in the movie.
You mentioned you heard Hunter's commentary:
What's with all the high pitch squealing throughout? What was he taking?
It was a hilarious commentary, but I'm afraid it didn't offer the insight I had expected. He was certainly one of a kind.

On a side note:
As much as I loved the novel, I really want to recommend "The Rum Diary" to everyone here. It's Hunter's first, and I dare say it is the most entertaining book I have ever read.