To activate the Mega-Stuffy, you first need to collect 6 individual plush toys:

• Unicorn
• Monkey
• Duck
• Giraffe
• Bear
• Elephant

You can find them in the following locations:

• Unicorn
  • The unicorn is located in the control center in a locker to the left of Stammin’Up. You’ll recognize the locker because it’s slightly open. Go to this opening and crouch down. Then, interact with the unicorn. If the interaction was successful, the plush will disappear into a small, reddish portal.
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• Monkey
  • The monkey is located on the connecting bridge from the Ocean Tower to the tech department, in the corner on the left side. Again, crouch down and interact with the monkey. If successful, this plush will also disappear into a small reddish portal.
  • 

• Duck
  • The duck is located on the shipwreck in a dumpster on the right side. Again, interact with it, and if successful, the plush will disappear into a small reddish portal.
  • 

• Giraffe
  • The giraffe is located on Crab Island next to a lamp, between the crafting table and the weapon that can be bought from a wooden plank. If interacting doesn’t work, you can also shoot the plush toy, and it will again disappear into a small reddish portal.
  • 

• Bear
  • The bear is located in the bio lab near the crafting table. Here, the same interaction applies: interact with the plush, and it will disappear into a small reddish portal, just like the other plush toys.
  • 

• Elephant
  • The elephant is located in the mining tunnel next to the GobbleGum machine. Once again, interact with it, and it will disappear.
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Once you’ve collected all the plush toys, return to the residential area. You’ll now see each plush toy on the beds. Interact with them again (each one will also drop some loot). After you’ve interacted with all of them, they will begin to float toward the center of the room and merge into a Mega-Plush. This Mega-Plush will then assist you in fighting the zombies for a few rounds.