What I loved: The illustrations really tell the story here, and I loved all the detail. Particularly the scenes at night are great, as the reader can see things Duck and Penguin cannot, such as the bugs, owls, and other nighttime creatures. The book manages to be not at all scary for the readers even though Duck and Penguin do get a bit scared. They do not say anything during the book, with only Betty and Maud cheerily chiming in throughout. This is an interested juxtaposition with what we see in the illustrations (their excitement vs. Duck and Penguin's unhappiness). I do really like that Duck and Penguin end up working together at the end a bit and there's some great humor throughout.
What left me wanting more: I appreciate some grumpy characters and am even OK with verbal conflict (when it can teach about conflict resolution). The part that I found a little troubling was the physical confrontations between Duck and Penguin, where one is shoving the other or pushing a pillow over the other. This is not spoken in the text and only appears in the illustrations, so this could go over little one's heads, but I would have appreciated more grumpy faces vs. pushing. This was probably due to Duck and Penguin being nonverbal and wanting to show the conflict, but this conflict is shown and the resolution is not full (no apologies because they don't talk, but we do see them working together).
Final verdict: Overall, this is a cute picture book about friends and not friends that is told primarily through the illustrations. Bright colors and fun details make this a fun book to look at and tell a fun story about a sleepover between two young girls and their stuffed animals.