You start off as a normal crewmate and you can do one of two things you can use different machines around the map to go skinny among us but you can also get really big by getting attack by the fat among us imposter. The fat imposter will feed crewmate with any food so they will be bigger and can't fit the door.

Remember if you get to big or fat you can explode, but if you complete all your task and you get to be the skinniest that you can, you can escape the stage.