All I know is that Terry Pratchett has made the exact same joke about zombies in two books--according to certain traditions, zombies aren't actually the dead; they're living people who've been fed a certain fish part and a certain rare root. This has given way to the "zombie fish and chips" joke twice. Also to speculation on both occasions as to how one determines such a thing.
"Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"
"You can't erase icing."
"I can't believe it doesn't work! I found it on the internet, man!"