Turtle's Penguin Day by Valerie Gorbachev
Turtle's dad reads him a book about penguins before bed. That night, Turtle dreams he is a penguin and has so much fun in his dream he decides to dress up like a penguin for school that day. He also takes the book to school with him. The teacher and his classmates all catch his penguin enthusiasm and they have a great day pretending to be Penguins at school. That night, his dad reads him a book about Monkeys...
The illustrations are sketchy and fun, the story is brief and engaging. This would be a great story to read to older preschoolers or kindergarteners.