Neighborhorde

This is relatively simple, you just need certain things to happen.

Firstly, buy "Camp Woody" in the shop for 250 tickets. Then, start a game on this map (difficulty doesn't matter) and look for the campfire on the far right. You will need to play until you get a ghost wave (was 3rd wave for me, but it's random). They look like floating animal heads. Just stand to the right of the fire so one of the enemies will float over the fire. The AI might mess you up here, but the heads have decent HP so will probably get far enough, just adjust your positioning so the heads pass over the fire.