So. I came up with a good theory. What if as a plot twist to the story, Carter broke out of jail, and came back to HLC this time with a different purpose. Maybe he would come back to visit poor Dr Alvah who was heartbroken when he left. Carter would come back in a different identity as his old. Though in my imagination, his name is really Carter Greene, and the girls maybe found out that he created other names that he used over time. But it would be interesting to see that Carter, as a changed human being, and being the adult man he should be acting as, we dive deeper into the past about him, finding out him and Dr Alvah share a past together, and (Another theory) that Kacey is his daughter, *thank you @LiviJay3 for the idea.*
But the complex part of this would be the age group. Now this show is made for mostly 6-10 year olds, and they would have to alter the age group to maybe 10-15 year olds because the content wouldn't be appropriate. Just saying, a six year old kid is not going to understand if a person had a kid by accident.
Most importantly, I like Carter as much as the main girls, so it would be an exciting thing to learn more about his actual backstory, other than reading the fanfics that I have created.
Thank you for your time.