Delay

We've determined that Hippo doesn't speak in complete sentences, but can ony give part of her me-ows at any given time. This of course raises the upsetting thought that there may be unfinished me-ows inside Hippo, waiting for the right moment to come out. I like to think that if that happens,  when everyone's asleep, she says softly to herself '-ow' before nodding off herself.