One of the hardest things I've had to deal with in my career is keeping my material topical even though I only release albums every three or four years.
There's a lot of different ways that a song would be a challenge to parody. There are a lot of songs that would ostensibly be a good candidate for parody, yet I can't think of a clever enough idea. Some songs are too repetitive for me to be able to fashion a humorous set of lyrics around. Some songs flat-out just don't work creatively for me.
I have very mixed feelings about it. On one hand, I’m concerned that the rampant downloading of my copyright-protected material over the Internet is severely eating into my album sales and having a decidedly adverse effect on my career. On the other hand, I can get all the Metallica songs I want for FREE! WOW!
I decided that I wanted to be a voice on every animated cartoon in the history of the world - even shows that haven't been on the air for a very long time, that's going to be harder to pull off.