Boxpeople are ironically people made of boxes.
Boxpeople are made of boxes that float into a bipedal, human-like form. They have fingers and toes made of strips of cardboard, and are capable of all 5 senses that humans do. However, they reproduce in a similar fashion to Krokkolakken, making cardboard boxes from trees and enchanting them. They are much more docile than Krokkolakken, however, and are allies of the Irken Empire. They are flammable, but otherwise impervious to any other attack. They hate Nightmare Irkens, though.
The Boxpeople are led by Door, a particular Boxman who can shapeshift into a door. The Boxpeople live in Cardlantis, a place presumably made of magical cardboard. Not much is known about Cardlantis, but it's evident it has technology. Often times they will arrive randomly in a battle to help the Irken Empire, or pretty much any Irken that isn't a Nightmare Irken. Whenever someone is taken to Clardantis, they are knocked out or given a sleep drug before travel. No one knows where Clardantis really is, but it seems to be a whole dimension made with types of paper and cardboard.
The Boxpeople speak Boxxi and English.
Link to a Boxxi translator: