Gadget's Plunger Shoes
Gadget's Plunger shoes allow her (or, presumably, any other rodent of similar weight) to walk along vertical surfaces, or upside-down on the ceiling. This capability is mirrored by the Rangerplane's plunger landing gear.
Zipper has been shown to have no need of plunger shoes, capable of walking on the ceiling without technological aid.
The plunger shoes appeared in Adventures in Squirrelsiting, among others. Could someone fill out the "others"?