This could all go horribly wrong and is your cat's idea of lunch with pudding, but Duplex, the fish-bird tank-cage by Constance Guisset is really wonderful.
Perhaps it doesn't go far enough though, maybe it could become a totem pole of increasingly neglected pets with a Russian Dwarf hamster named Hammy at the top who hasn't eaten for weeks.
No that would be cruel. Everyone knows Russian Dwarf hamsters must live in pairs.
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