Similar to the Winnie the Pooh theory, each main character is a representation/suffers from a mental illness. For example,
1. Max has antisocial personality disorder- He already shows several early signs of developing this condition such as disregard for authority and the feelings of others. He also shows violent tendencies when he does not get his way
2. Emmy has narcissistic personality disorder- The evidence for this comes primarily from two episodes: In Emmy's Dreamhouse, Emmy constantly tries to build/change the treehouse into what she wants. The other episode is Tales You Lose in which we learn that Emmy does not take losing well. Those with narcissistic personality disorder often have a sense of entitlement and being the best of everything, even when they are not. They always have to be right which is something Emmy has in these two episodes in particular but can be seen throughout the entire series.
3. Ord has Generalized anxiety disorder: He is afraid of many things, constantly worries, and often overthinks the worst case scenario. He often needs a lot of help relaxing and staying calm when he is afraid of something. People with this sometimes have coping mechanisms or ways to calm down. His turning invisible manifests itself in this way.
4. Cassie has Social Anxiety Disorder- Cassie's anxiety is more geared toward a fear of messing up/being humiliated. She is also described as Shy in the opening song. This explains why she often does not speak up, she is afraid of being embarrassed. She shrinks when she gets upset which means that she feels much smaller than everyone even when she's not.
5. Zak: OCD- He is very obsessed with order and cleanliness. He also does not like dirt which is something many OCD people do.
6. Weezie- ADD/ADHD- She is constantly hyper and talkative. This is something that often gets her into trouble and annoys those in her company. Her behavior also causes her to make reckless decisions.