The Catgirl Dolls Ending is an Ending in Prisoners of the Elder One. It occurs after using the Transfigurative Orb on Tiffany while she's still a catgirl slave.
The spell fails multiple times, due to Tiffany's lousy willpower. Upon some unfortunate phrasing from Erik, the Orb transforms the two into catgirl sexdolls. While they aren't under The Elder One's control, their nymphomaniac nature means they spend less time escaping and more time screwing.