Miss Hoppy - though not a cat - did this a few times. She did not like going to the vet, though she didn't particularly mind the carrier. Once at the vet's office, she was eager to get out - while in the waiting room. But once in the exam room, she'd hop out, but then that nasty white-coat would do all manner of unspeakable things - like touch her feet, etc., and she'd do anything to get back in. It was a "safe cave" from the nastiness. And once home - hey, it was still a safe spot, in case WE had any thought of doing something horrible like giving her medicine. Immediately following a vet visit, the carrier is a "safe cave" instead of a "transport to torture" device.