Effects Guide (incomplete)
Car
When you enter the Nexus for the first time, a NPC will enter the dancing robot world. Follow her into the door and go north until you see a road. Interact with the car to retrieve the effect.
Zombie
Enter the door with the pyramid on it and head east until you find a purple entrance. This should take you to a desert, where you'll find a dead body. Interact with the body for the zombie effect.