How do you come up with parody ideas?

Here's what ApologetiX lyricist J. Jackson had to say about the subject in an interview with "HM" magazine in 2004:

There are basically three ways we might end up doing a parody. The first way is you pick a song that's popular and try to think of a good spoof -- a Biblical angle with words that rhyme with the original, especially in the opening lines, the chorus and the title that somehow captures an aspect of the original.

A good example would be "Enter Samson" our parody of "Enter Sandman" by Metallica. You hear that title and you instantly get a picture, and Samson is a character that just seems to fit into the whole Metallica image. He'd probably be a fan of their stuff if he were around today. Plus he knows what it's like to have long hair, get it cut short, get made fun of, and still have the last laugh, coming back stronger than ever, just like they did!.

The second way would be you pick a topic and look for a song that fits it. For example, "What song has a word in it that rhymes with Mephibosheth?

The third way is you're minding your own business and this great parody rhyme just pops into your head, for example: "Naomi Gonna Be With Ruth," our parody of "Only Wanna Be With You" by Hootie & the Blowfish.