During the "Apply It Up" interviews, both of the girls' confessions. Basically, CeCe knows she won't ever be the best student in school, but she gets to be a genius on the dance floor. And Rocky reveals, after annoying the interviewer by talking about CeCe, that when she hit her growth spurt she was constantly bullied, but it's only when she dances that she feels better about herself.
Rocky: Call me names like "Giraffe" and "Tree". (paraphrasing)