I have had fish, hermit crabs and a turtle. Many other teachers have gerbils, mice, snakes, hamsters etc… I have found real creatures can be REAL maintenance. And what do you do with them over the long breaks? How about the unexpected snowstorms? Not to mention, schools are revisiting health and safety policies that won’t allow certain animals in schools anymore.
So one year I got an invisible dog and allowed the kids to name him. He had a visible bed, toys, food and water dishes. He was well behaved and never had accidents. My first graders adored him. They took him to recess and even on errands to the office. I put books about dogs (both fiction and nonfiction) by his bed, in case students wanted to brush up on their canine knowledge or read him.