The question is incomplete and the full version can be found online.
Answer: The mood is lighthearted because the comparison created is silly.
Explanation:
A simile is a figure of speech that proposes a comparison of two different things to create a more vivid description of something. In this example, the reference to the pillow shaking like "pudding on a plate" creates a playful image of the movement of the pillow caused by the cat.
The comparison is simple, not difficult to understand. And the mood, despite seeming a reproach to the cat, is not angry. It´s not happy either, as the author gets disturbed while sleeping, but the reproach is playful and still warm.
