The combined forces of all the mulitverses stood arrayed against their common enemy: entropy. "I think entropy's winning," one leader whispered to another. "Good thing it's slow."
What's the smallest?
By one extruded pseudopod at a time, the single-celled organism oozed forward across the slick surface, until it came to a thick black line that halted its progress. It stopped before the line, stymied.
Kim lifted her head from the microscope. "Teacher! I think there's a hair on my slide!"
(I could spend all day trying to think of bigger and better, or smaller and more minor, to top these, but I think at some point I am defeating the purpose of this as an EXERCISE. I already think that my whole response to "Imagine That" rather missed Vorhaus's point, which was to be imaginative without constraint or worrying about details.)