His owner bought Milk in the Half Gallon, and he drank many saucers full every day. Many. Many many many. Every day.
One day his owner decided to buy a Quart container instead, since the Half Gallon was juuuust a wee bit too much Milk to get through. And when she poured the new Milk into the saucer, Willow wouldn't drink it. It just sat there.
The owner drank the Milk and found it to be fresh and good, so thought maybe Willow wasn't feeling well. She went out and bought a fresh Quart just to be sure, but he wouldn't drink that either. So she decided to do a little test. She poured it into the rinsed out (with just fresh water, no soap) empty Half Gallon container (and didn't let Willow see her do it). And then proceeded to pour the new Quart, disguised as a Half Gallon, into the saucer. But Willow still wouldn't drink it! He knew it was from the evil Quart container. Even though it was the same brand of Milk, from the same dairy and the same store. Something about it (undetectable to human senses) was different.
So the owner, because she's a little wacko, went back to the store and bought a brand new Half Gallon jug. All the while thinking, "This is ridiculous. Truly, I have lost my mind". She poured it into the saucer, and lo and behold, Willow dove in and drank it all up. And asked for more!
And now the owner has a refrigerator full of Milk - the old Half Gallon jug full of 'Quart' Milk, which she has on her cereal, plus the new "Willow approved" genuine and true Half Gallon jug. The Other Cats who live in the House don't drink Milk at all, so the owner is making a lot of Milk-inspired recipes, and is in no danger of developing osteoporosis for the foreseeable future.
~ THE END ~