How to pick a subject for your parody

If it is not healthy for the characters, it is not healthy for anyone.

In general, what you want your parody to be about pretty much comes down to you, and has to be self-guided. However, there are some things to make sure of understanding. Mostly, there needs to be a balance between what you want and what suits the song.

First tip: Do not choose your topic based on something that has nothing to do with you

It is good to know your area of expertise and choose topics accordingly. Writing things anyone could have thought of does not do much for you. But I know this does not seem to mean much when I put it this way, so I am getting to an example.

The Styx song Lords of the Ring is a song to which the obvious thing to do is, of course, Lord of the Rings. If that is the franchise you already wanted to write a parody about, this is the song for you. But if you never had an interest in writing song parodies about LotR, doing it now just because it is the only easy thing to do with said song is not advised. Lord of the Rings is a parody of that song anyone could have come up with, after all, so what would doing that get you?

(One of my personal rules is that Pirates of the Caribbean is the only topical thing I allow my parodies to cover. One of the reasons for the existence of that rule is that I find it helps keep me creative and out of potential traps like the one just described.)

I can also help you understand what parodies anyone could have thought of can feel like, and why they can be a problem, with this page, particularly under the headings Why did you bother to change father? and Unfunny life.

Second tip: Do not choose your topic based on something that has nothing to do with the song

If there is one thing a parody should never be, it is arbitrary. You need a good reason to be marrying the parody subject you are to the song you are. As noted above, having general ideas for topics in advance is necessary, but nothing should be set in stone either, until you know which song you are doing.

If you are just telling the stories you want to tell and using existing tunes as if they are all the same to you, you have no reason to be writing parodies and should consider writing your own tunes, or to no tune at all. Simply taking an album you know and, at random dates, taking whatever is the next song in the album and making it about whatever is the latest thing that happened, as the Comic Five did, is not advised. You can see why from their their discography page.