To make the shelf I used 3 dowels- cut them a bit longer than the width- and then used a dremel to make a notch for them to sit on the bar of the cage. I cut a piece of Coroplast and put it on top of the dowels. You could use anything lightweight- like sturdy cardboard, etc. And then I put a fleece blanket up there for him so he does not slide when he jumps up there- since Coroplast is slippery. It pops into place in less than 30 seconds but is lightweight and easy to clean.
I used this with my other bunny Penny before and she occasionally would knock a dowel out of place- but nothing was heavy enough to hurt her. And I am sure there are ways to secure the dowels and a heavier shelf if that is used.
Poor Griffin will be confused- he lives in a dog crate, in the cats room, listens to the parrots whistle all day, and sleeps on a blanket that says “Dog”. I plan on moving him into the room with the other bunnies soon. I think I am no longer fooling anyone and they know he is somewhere in the house. Cotton and Schroeder have been leaving extra poos outside the cat room door- and I am pretty sure someone wee’d under the dining room table.