This will require more evaluation, but it's possible that, after watching my new cats in action for a couple days, they are Felix and Oscar.
I've been using wet food to try to lure them out of hiding and into my lap (or at least into petting range). Gumbo sees the food, stuffs his face as far into the tub as possible, and starts slurping it down. And when he eats the dry food, he manages to scatter some of it around on the floor. And the paper under the water bowl is wet. He totally seems like the kind of cat who would, if he had opposable thumbs and enough strength, drink the milk straight from the bottle and not notice that it's a few days past its expiration date besides.
Beanie, on the other hand, delicately licks up the food, moving slowly and deliberately. He washes up after meals (and at other times). If he could talk, he gives every impression of a cat who would ask for a tablecloth, cutlery, and a flower in a vase to bring his dining experience up to an acceptable level. He is also fastidious in using the litter box, covering completely and then knocking his paws on the edge of the box to avoid tracking litter.
But it's too soon to tell if these are their usual behaviors or the result of being in a strange environment. Their default positions are still "in hiding", though Beanie actually explored my office with me in it to watch today, so that's progress.
Both of them purr at length and fairly loudly, by the way. The medical notes I got said, for both of them, that the vet couldn't clearly listen to their lungs because of the noise.
I've decided that Felix and Oscar aren't the right names for the cats; the initial behaviors that prompted them haven't continued. I'm currently leaning toward Orlando and Giovanni, which pass the random-friends-and-relatives test and the neighborhood test (would I be embarrassed calling an escapee?). A pair of perfectly-nice Italian names will suit, and if you happen to know that I'm a fan of Renaissance music, you might correctly detect a further inspiration for those names in particular. :-) (Orlando is the brown one, who's also the lovey guy who sleeps in my lap purring loudly.)