When artists or writers make "zombie versions" of famous pop culture images or stories is it considered parody and copyright is ignored?

Parodists have a legal right to use previously released works in the US as the basis of their own without fear of lawsuits, as it falls under Fair Use.
Thank goodness. I love Weird Al’s “White & Nerdy.”

I do not know the laws of other countries, however.

VIVA LA DEAD poor old Che, you can spend your life fighting the evil forces of capitalism and still end up with your face on a t-shirt in every GAP Store on every corner.

You know, in that Che graphic, the eyes were moved! In the real photo, he’s looking down at a dead compadre at the man’s funeral. Some Irish graphic designer moved them upward so he’d look more noble.

I hear they had to resurrect Jane Austen to legally publish Pride and Prejudice and Zombies. Wormland Security was really breathing down their necks.

I should get started on the zombie Mario t-shirt design. Or zombie Darth Vader. Zombie Mickey Mouse would be awesome. I should rephrase this question to: “What pop culture icons would look really cool if zombified?”

lady gaga?
mohammed?

If I’m lucky zombies will come back in fashion and vampires will fade out again. To specifically answer your question, I think that it isn’t so much parody. Copyright isn’t being infringed as it isn’t really plagerisim. Aprilsimnel said it wonderfully.