This is from The Sandman #18. It's written by Neil Gaiman and illustrated by Kelley Jones.
This tale begins with a small, white cat being called by another cat to sneak away from her house one night. They speak of an event in a graveyard that they don't want to miss. When they arrive, they see that many cats are already there. A Siamese cat comes to tell her story.
The Siamese cat has a dream that where she enters a boneyard in the Dreaming. In the dream a raven with no skin on its head informs her where she can find out exactly why the humans killed her offspring: a cave inhabited by the Dream Lord. After a long travel the Siamese cat makes it to the entrance of the cave, where many fearsome animals tell her to leave. She responds by saying that she will only state her business to Dream. Inside, she finds Dream in the form of a cat.
The human tells the other humans that "dreams shape the world," and that if enough of them dreamed it they could change the world so that they would become the dominant species.
The Siamese cat tells the other cats how she left the humans and traveled the world, spreading her message wherever she went. At the end she says "Dream the world. Not this pallid shadow of reality. Dream the world the way it truly is. A world in which all cats are queens and kings of creations. That is my message. And I shall keep moving, keep repeating it, until I die. Or until a thousand cats hear my words, and believe them, and dream... and we come again to paradise." As the cats all leave, the white kitten asks the older brown cat if he thinks it will happen. The older cat responds "Little one, I would like to see anyone--prophet, king, or god--persuade a thousand cats to do anything at the same time. No, it will never happen."