In Malouf's poem "Eternal Moment at Poggio Madonna," how does Malouf make the ordinary extraordinary? How does Malouf expand playfully on the simple childhood sentence, "the cat sat on the mat," in the first stanza? Why do we personify our domestic creatures? What are the key ideas in this poem?

The first thing you might notice about how Malouf plays with the phrase "the cat sat on the mat" is that he takes rhyme and turns it into alliteration. The repetition of the hard c sounds in "cool reclusion curls" and "creaturely comforts" delights the reader in the same way that a child is delighted by the rhyme in "the cat sat on the mat." It is also not obvious until the second stanza that Miss Mischa is a cat: once this becomes clear, we can go back and re-read the first stanza in a new light. By doing this, we get the emotional reward of having "figured out" the meaning of the first stanza and realizing the allusion he has made.
Malouf makes an ordinary event—a cat lying in the sun—extraordinary by implying that the cat can sense some kind of supernatural or mythological glow in the sun's beam. Malouf tells us that the cat has not just wandered in and plonked down in the warmest spot in the house for its temperature alone: they've made a calculated decision based on a variety of factors. In doing this, he makes an allusion to the many mythologies which saw felines as gods, most famously ancient Egyptian mythology. He's telling us that the cat has chosen this specific "mat" to "sit" on for reasons "nature or the eye" could not understand.
This ties into the reason we personify domestic creatures: they hold a special place in our hearts, and we care for them, but they are incredibly mysterious, and their motivation and behaviors can be confounding. While we can definitely communicate with animals, we can never fully understand them, nor can we make them understand us. Humans understand things more easily if they remind us of ourselves; if we imagine that a cat has human-like qualities, they will be easier for us to understand.