I have made no secret of my love for Zombie Jesus Weekend and my belief that it should be an atheist holiday. Judging by the number of zombie parades, parties, and the like, many atheists feel the same way. I'm sure some of the fun has to do with the broader love of zombies, but I'd like to think that Zombie Jesus Weekend also provides a perfect excuse to celebrate our escape from the clutches of faith. That is what makes the holiday so perfect: it is an ideal blend of silly fun, an excuse to acknowledge how absurd the whole Jesus-returning-from-the-dead thing really is, and an opportunity to reflect on our personal journeys to atheism.
The image of a decayed Jesus corpse emerging from a tomb to munch on the brains of believers really is a great metaphor in many respects. You've got the fun observation that if Jesus really did come back from the dead, this would make him a zombie. You've got the munching of brains as saying something about how Christianity (and faith in general) afflicts the mind. You have the spread of the zombie virus from person-to-person and the similarities it bears to the viral nature of religious belief. You have the highly resourceful nature of the holdouts - small groups of uninfected survivors banding together to oppose the infected hordes. You get the idea.
Some will protest that celebrating Zombie Jesus Weekend amounts to little more than mockery of the Christian faith. It certainly does have that aspect to it, but I do not think it has to be so limited. And besides, there may be some value to poking fun of absurd beliefs from time to time.