Turns out, it was an earthquake (2.7). You might scoff at the idea that K jumping up on the bed was comparable to a ground-shaking seismic event, but she had a special talent. She was not a large cat, when she thought kitty breakfast time should be NOW, somehow she seemed able to increase her mass. Perhaps she spent a minute focusing her Chi. She'd land on the bed so vigorously, one would have the heart-stopping certainty that a Sasquatch had materialized just below the bedroom ceiling and fallen onto the duvet. Then she'd stomp around our heads, purring so loudly that the pillows shook. Unfortunately, she'd never wear the watch we bought for her, so her wake-up visit could happen hours before my alarm was set to go off.
I'm glad it was merely an earthquake, actually.