A couple of days after we adopted Melvin, his seed cup fell down on it's side. He immediately saw it as a nest, and since that day, he loved cups. He didn't take all cups though; it had to be dark, warm and cozy. Took me 5-6 cups before I gave him the dice cup, which is made out of faux leather and is coated inside. Boy has always been picky. Mel at six/seven weeks old.