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.
TV
In the dancing robot world, there is a large television set. Enter it and wander around the world until you find a unique TV set. Interacting with it will give you the effect.
Fire Extinguisher
Enter the door with the florence flask on it (southernmost from the Nexus). Enter the Lab, the building with the blue dome slightly south from the entrance from the Nexus and go through the double doors on the ground floor. By navigating the ground floor corridors you will find a fire extinguisher, which you can interact with to get the effect.
Golf Club
In the dancing robot world is a large machine. Interact with it and be transported to a lab in a neighborhood. In one of the houses is a set of stairs. Go down the stairs and interact with the golf club.
Paper
Enter the door with the paper airplane on it. Go north until you see vertical paper(with shadow), go west until you see vertical paper's shadow. And go north you see the paper with blue paints. Interacting with it will give you the effect.
Long Hair
Enter the door with the bloody hand on it. Travel directly south and you'll see a white patch with a mannequin in the centre. Interact with it to get the effect.
Weather
Enter the door with the bloody hand on it. Go south west until you find an arm in the ground that is completely black and white. You'll find yourself in a White Desert. Look for a monochrome sun and interact with it to take you to a world with blue grass and wandering rock-like NPCs. Located somewhere in this small-ish world is a cone surrounded by 4 panels. Interact with it to get the effect.
Potion
Enter the door with the florence flask on it (southernmost from the Nexus). Located in a north-west direction from where you entered is a pink potion bottle. Interact with it to get the effect.