Can I keep him, please?
We had a reading story called "It's Probably Good Dinoaurs are Extinct." The story concludes with a kid asking mom if he can keep a dinosaur as a pet. I had my kids write a letter to their parents asking to keep their favorite dinosaur as a pet. They had to give three reasons (three detail sentences) why their type of dinosaur would make a wonderful pet. We spent a lot of time brainstorming ideas, and the kids had a lot of fun with it.