The Popcorn achievement is a secret that you can unlock in Little Nightmares II. Amid the doom and gloom within Tarsier Studios’ horror adventure title, it’s a fun little achievement or trophy to acquire, which you will need to achive 100% completion. It is worth 30 gamerscore or a silver trophy, and it is easily missable if you aren’t paying attention.
You can get the Popcorn achievement during chapter three, which is the hospital section. As part of the fuse box puzzle, you need to open the locked gate on the left side of the first floor. Using a fuse you obtain from the right side, you can unlock the gate. In the room that joins the lobby to the hospital cells, you may have noticed some corn sitting on a plate on the floor. Pick it up and head downstairs.
Run to the elevator on the ground floor. It will take you to the incinerator in the basement. Throw the corn into the pit and pull the lever next to it to ignite the fire.
Wait for the process to end. The incinerator door will open. Climb into the chamber to see that the corn has been turned into popcorn.
The achievement or trophy will pop as soon as you see it, which has the tagline ‘Movie night on the ward – all taken care of!’.