What is a hypothesis? It’s a supposition made upon something based on current (limited) information. That is, a statement that might or might not be true, but if only the original facts (information) are taken into account, it cannot be proven wrong. If you know humans can talk and that humans cannot use magic spells, can you say humans can talk to other animals? Based on those two statements you can’t say they cannot. So, in a universe where only those two statements are true, another third one like that can actually be true.
So what’s a hypothetical universe? It’s basically a creation built upon a set of basic truths: a different world from ours, in which you decide what information from this world is true, and what isn’t. So, basically, is a universe based on this one, with changes, like a different gravity force, different colors or something… different. Anything. Are you up to change the world you live in? Of course, with your imagination.