Now yours on the other hand is meant to be funny read, not sung aloud, so you in MY opinion, you need to stick closer to the original phrasing and rhyme scheme of the song to be funny. Frank Jacobs of Mad Magazine was the king of this type of parody. The reason is, the reader is singing the song in his head, it doesn't work if the lyrics don't scan. In a "performance" version, the 'chipmunk' is doing the singing so of course it works, there it is for you to hear, you don't have to make the lines fit in your mind. Its a bit of apples and oranges. And, in a performance tape the delivery, instrumentation, inclusion of bits of other songs, narration and spoken parts, all work. If you just read my transcript, it loses a great deal of the humor. Where-as Mark Twain read aloud is not that much funnier than read to yourself. Its 2 different writing techniques. That's exactly why I didn't write a song first, I mostly made it up line by line as I recorded it. The bulk of the time creating that was figuring out the 3 part harmony on the vocals and mandolin part. The actual lyrics took only minutes.
As I said, this isn't my first rodeo, we had to create a parody of the scandal or news of the day and get it on the next morning's show or it would lose relevance. We got a flat $50 IF they used it, no residuals if they played it over and over. The other side of the coin was it was a user fee only, we mostly composed original melodies, not take off of existing songs, as I explained above that would have led to legal hassles on copyright and clearance. However, we retained the rights to the song in case lightning struck, as it did for one of my buddies.
He wrote a parody song called "Love Behind the Mini-Blinds" about a Tampa couple making love in their apartment with the blinds open, they got arrested, it made national news. He did a quick-one-off parody song, it got used on the morning show then later on Inside Edition, and indy record company pressed several thousand and he had a regional novelty hit and pocketed a few thousand dollars. This is the advantage to doing it on a user-fee basis. My partner and I wrote literally hundredsl, mostly throw-aways that I didn't even bother to keep copies of. I do have a couple dozen I thought were pretty good.
I've done the same with commmercial jingles "One Hour Optical, its guaranteed, One Hour Optical, for fashion and Speed!". Not exactly music for the ages, so I dont' always keep a back-up.
You have FReepmail.