Ok this might be a silly question but I'm curious.
I've always liked Thing's boxes and I'm wondering do you think the boxes were there in the house BEFORE Thing came to live with the Addamses and he just inhabited them and took them over when he came to live there, OR do you think they are HIS and came with him?
I think that Thing just takes advantages of various boxes and openings that are already in the house. Somehow, he's made them his own by creating a secret world beneath them that connects them all, and this is what we will never know about and that is part of the mystery of the show! After all, he can pop out of pretty much anything, even the umbrella holder by the door. At the same time, he obviously has one or two favourite boxes where he hangs out most often, and these may have been procured specially for him by the Addamses. Interesting question :)
I was always faschinated by the boxes, I used to make them out of shoe boxes and Kleenex boxes as a kid, now I have them made out of wood :) replicated the best I can.