The kitten said, "I don't like water, And yet my mistress's Little daughter
Shoves me in the tub And spoils my fur. (I know she'd cry If I did it to her!)
I can bathe myself. So can any cat. There's no excuse For things like that!
I ought to complain. Yes, but how? When they don't know the meaning Of meow?"
A kitten is stuck in a very unfair situation, and the whole poem is its complaint about it. The little daughter of the house keeps putting the kitten in the tub, which it hates, and it feels she wouldn't enjoy the same treatment herself. The kitten's argument is simple and sensible: cats clean themselves perfectly well, so the bath is pointless.
The fun comes from how seriously the kitten takes all this. Its logic is tidy, almost like a small lawyer making a case, and its indignation is easy to sympathize with. Then comes the twist at the end. The kitten knows it should speak up, but it has no way of being understood, since humans can't read "meow." The mood is light and playful, but there's a gentle note of helplessness underneath, the feeling of being powerless to explain yourself to people who simply don't get it.