I am sure someone could make some money out of this one.
My lovely wife bought our two Jack Russel’s new dog baskets which are basically a canvas / wood construction. Although the dogs loved them they actaully took up a fair amount of space. The idea was to turn them into double bunk beds to halve the foot print.
As they have a wooden frame it was simply a case of screwing the legs together using a small block of wood. The result works really well – old man Oscar sleeps at the bottom and the young upstart Daisy takes the top. I can only see it being a problem if your dog cant jump up – since our Daisy is regularly caught on our much higher bed this isn’t a problem.
Here they are trying to look cheerful (actually bit suspicious of bosses intentions as it is nowhere near bed time) :