Yes, you do have to dress like a zombie. Those who do not do so are welcome, but risk having their brains eaten by confused zombies. You have to admit - they're not all that smart, but they know a good living brain when they smell it.
Potentially useful things to keep in mind:
Causes of zombie-ness:
As everyone knows - or should know - zombies are usually attributable to one or more of the following:
Of course, there are many more possibilties. Be creative. Corpses in all stages of decay are encouraged.
For the low-budget zombie:
Zombie Walk?
Walk Like a Zombie
Recipe for Disaster
Zombies in the News
Curiosities
Spread the Virus
Contact
Walk like a zombie!
Zombie Walk 2005
photo gallery!