Ivan's coat leads to a hammerspace which usually takes the form of a shop/house. It's a recycled concept for an older OC (a dragon). At the time the house was interchangeable with the dragon OC's belly. The theme is fun and I kinda wanna hang onto it. So wall maw? He treats it like a disposal.
https://www.furaffinity.net/view/52084408/

The wall maw is a hammerspace within the hammerspace. It just defaults to this checkered upholstery.