My brother's theory of cat gravity, as developed with the help of Pippin, Lucas and Trillian:

Cats control gravi-
ty, that's why the light lap-cat
Gets so hard to move

Cats get heavier
With sleep - a 9-pounder can
Weigh 50 mid-nap

This is why three cats
On one large human can weigh
Too much to move off

Cat gravity can
Account for more late days than
Power outages.