Dexter first meets the Utoniums at age ten when he comes over to their house to discuss science issues with Utonium. Dexter soon finds himself bonding with the Professor and his triplets. At home Dexter has no friends and his parents are completely apathetic to his genius, but Professor Utonium understands him in a way other adults do not. Dexter finds himself growing closer and closer to the Utoniums as time goes on, but his relationship with his own parents seems to be getting worse with time. Can Dexter ever get his parents to understand him?
Set a few years prior to the invasion, Invisible Sun tells a take on how Dexter created DexLabs and how he became friends with the Powerpuff Girls.
Invisible Sun provides examples of:
- Ambiguous Disorder: Dexter is a loner with No Social Skills because other kids his age don't "get" him, he was nonverbal until age three (according to him, because he spent the entire time silently learning), and he's been a child genius since birth.
- Big Brother Instinct: The normally gentle DeeDee does not take kindly to people bullying or looking down upon her little brother, not even her parents.
- Calling the Old Man Out: Chapter's 20 and 21 revolve around Dexter confronting his parents on their neglectful behavior, with the Professor's help. Even DeeDee calls their parents out.
- Conspicuous Gloves: Dexter wears his lab gloves even to dinner. The girls find it unusual.
- Expecting Someone Taller: The Utoniums are surprised to find the reclusive scientist Dexter is no older than a 4th grader.
- Free-Range Children: Dexter came all the way to Townsville on his own. Utonium concludes his parents don't care much for him.
- Hidden Depths: Ms. Keane is a kindergarten teacher with a degree in physics.
- Kids Are Cruel:
- Due to being a Child Prodigy with a Friendless Background, Dexter has to deal with a lot of bullying at school. When the Gangreen Gang kidnaps him and attacks him, he isn't phased because he's been beaten worse at school.
- Olga is only in third grade but loves to bully Dexter (but only when his sister isn't around)
- Last-Name Basis: Utonium's lack of a known given name is lampshaded when Dexter is asked Professor Utonium's name and can only think of "Professor".
- Named by the Adaptation: Utonium's name is Patrick Lawrence Utonium.
- Parental Neglect: The theme of the story revolves around Dexter feeling neglected and looked down upon by his parents. They ignore him and don't take him seriously at all.
- Parental Substitute: Professor Utonium is like the father that Dexter has never had. Dexter isn't used to having parents that take him seriously or friends who understand him.
- Promotion to Parent: DeeDee often took care of Dexter as an infant because his parents would ignore him a lot.
- Unexplained Accent: Dexter's accent confuses Ms. Keane, who mistakes the American-born kid for Russian.
- Wanted a Son Instead: Dexter was an unplanned pregnancy. His parents had hoped for a second daughter instead of a son.
- What the Hell Is That Accent? : The Powerpuff Girls try to figure out what Dexter's accent is, but they're unable to place it.
- Who Names Their Kid "Dude"?:
- When Dexter says his friend's name is "Professor", his parents reply that it's an odd name.
- Dexter and DeeDee consider their own names unusual.