i just introduced the cats to patches one by one (really carefully- he was cupped in my hands and just barely peeking out) and they were fascinated by him at first. they stared at his cage constantly, but i wasn't worried about them getting into it cause i have an aquarium with a screen lid that slides into the frame, plus i got a heavy, coated wire mesh lid that folds in half to put over top of that, just in case.
he got out of his hamster ball awhile ago and we were frantic, but the cats didn't seem to think anything of it.
now i tape the ball shut, just in case.
once in awhile our littlest cat will observe the hamster in his cage, and they'll lay on the cage now and again, but other than that, they don't pay him much mind.
patches is oblivious top the cats. it's cute.
i can let him run around on the floor and the cats just pass on by. 'course i'm right there with him.