The story starts out with Riley having a pretty happy day. She got an 'A' on her science report, her team won their hockey game, and she got to have pizza without broccoli for dinner. That is a pretty great day.
Chapter 2, Meet the Little Voices
Joy, as leader of the emotions, comes up with the best solution to deal with Riley being able to hear them. By speaking to Riley as she nods off to sleep, Riley will either write their conversation off as a dream, or will freak out less if she hears them the next day. Any other plan the emotions thought of would've hindered their ability to fully guide Riley.
Though Riley believes she's having a dream while she talks with the emotions, she's completely accepting of all of them. She playfully jokes that she can blame Anger for whenever she gets mad and gets in trouble, she accepts Sadness as one of her emotions even though Sadness hasn't really guided her all that much throughout her life, and wholeheartedly agrees with Disgust about broccoli to the point of saying the exact same thing as her.
In the same moment, Fear manages to muster up the courage to speak to his host. Considering he's Fear, it's a pretty big step for him.
Chapter 4, You Mean I Look Like Broccoli?
Riley and the emotions bond over their conversation of the Mind World as Riley draws. As she learns more and more about the Mind World, the more she wants to see it with her own eyes.
Joy and Sadness when they come up with a way for Riley to visit the Mind World. Sadness just laments how Riley's desire was just hopes and dreams, and it's those key words that allow Joy to come up with her idea, remembering what she had seen on her and Sadness's adventure.
Sadness: "I guess it's all just hopes and dreams..."
Joy: "Hopes and dreams... Hopes and dreams! That's it!(hugs Sadness) "Sadness, you're a genius!"
Chapter 5, Lucid Dreaming
Sadness manages to find information about lucid dreaming in the mind manuals, claiming that the section it was in was so short she almost missed it. Since she's read all the manuals, she would definitely know where to find important information on short notice.
The fact that the mind manuals had a section on lucid dreaming without the filter and exploring the mind. Those books have information about everything. And the way it's written makes it sound exactly how it would in the film, showing that the author really has shown her work.
Upon hearing about the dangers of Consciousness Tampering, Fear is quick to volunteer to leave Headquarters in order to keep an eye on Riley. It also doubles as a moment of Heartwarming.
Disgust manages to persuade the mind workers to let Riley try out lucid dreaming by pointing out that she and the rest of the emotions know what is best for Riley, and Sadness points out the mind workers' own desires to see Riley as well.
Shortly after, Riley achieves lucid dreaming on her first try.
To be fair, this is a universe where people's dreams are designed by little people living in their minds. Being aware of the existence of these people, and having the ability to communicate with them, would no doubt make controlling one's dreams a lot easier.
On accident, Riley manages to create white memory orbs, along with a white core memory.
The white core memory itself creates a new island of personality which Riley names Possibility Island after the fact that it was with the emotions' help she was even able to enter the Mind World and experience things beyond her wildest dreams (or at least her previous ones.)
Chapter 12, Wavering Focus
Despite seeing all that Tracey saw with Riley, Ann still steps up to defend Riley after Fear leads Riley to run away from her friends. That's the sign of a true friend.
Jordan is also a true friend. He doesn't know what Riley, Ann, and Tracy are talking about, but he still stands up for Riley regardless.
Chapter 14, Pure Imagination
Disgust holding Riley's Imaginary Boyfriend to a higher standard than Riley set originally. It's especially satisfying for the adults reading to see Disgust demand that he get a personality before Riley accepts him. Looks like someone already knows what really matters in a relationship.
Fear goes into Skydiver mode when Riley accidentally cuts her flying seeing her imagined memory dump. Landing safely on the ground, and then catching Riley despite her being a good half foot taller, and getting smooshed in the process. Let it never be said that just because Fear's afraid doesn't mean he can't do amazingly brave things in the process.
Chapter 17, A Hole in Her Heart
On a pure whim, Riley jumps out of the Train of Thought and starts flying. At the discovery that her Reality Warper abilities aren't confined to Imagination Land, she teleports herself and all the emotions to their next destination with a single thought.
The way Riley seriously engages with the emotions about whether to bring back Bing-Bong is very mature for a 12 year old. Almost like how her experiences with her emotions is also maturing her emotionally. Hence how she's able to use the experience to not only talk about "living up" to another identity, but about how to deal with Death in her life (even if it's just in her mind). That takes a lot of maturity to step away from doing that, and it's awesome to see Riley taking that kind of responsibility so seriously to make that kind of decision.
Chapter 19, A Talk With Mom and Dad
The whole scene where you see Jill's emotions react to seeing Riley's drawings of her Mind World. We've seen emotions react to things like that before (see chapters 10 and 11), but this is the first time there's no denying she actually knows about it.
Chapter 20, Mixed Emotions
When the test comes back, Riley immediately summons up the courage to admit her cheating, repairing Honesty Island. And she did it completely on her own as the emotions have been locked out of the controls.
