h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

The suggested cat rotating levitation drive system (which is, of course, what happens when you do tie two cats back to back and drop them) can be made more efficient by replacing one of the cats with a buttered slice of toast. Since toast always lands butter-side down and cats on their feet, the resulting combination hovers just above the ground, spinning...

I know about that but I think it would look funnier with two cats. And also, what if a cat and buttered bread don't rotate at the same speed? then it would get all lopsided. Since the cat is heavier then the bread, I would think that the cat would just rotate to feet first and fall the rest of the way with the bread on its back. For the rotating levitation drive system to work properly, you would need to either have two cats tied back to back, or two slices of bread glued together.

Ah, but what if the two cats were particularly flexible and managed to come down on their sides, getting a couple of paws down each?
I suspect that the extra weight of the cat would be overcome by the annoyance factor of the toast. After all, cats landing on their feet is largely an indifferent event (unless you're the cat of course ) but losing your bit of toast and having to scrape butter off the floor is especially annoying and therefore, perversly, more likely to happen.

The problem of the cats flopping down into the side by side position can be overcome by placing two side panals next to the cats so that they have no choice but to continue rotating round because the side panaling would not allow the cats to move from side to side without continuing in a continuous rotation

Perhaps these side panels are where the toast should make an appearance?
A two-cat only mechanism is going to spin in a highly jerky manner. The addition of the toast might serve to smooth the action of the overall system.
There is however still the danger of the cats falling forward or backwards. Scope for further design work there perhaps?

Yes, of course
We must make sure the mechanism is properly balanced so that the cats can properly miss the ground and stay in the air