Continuity mistake: When The Library Kid speaks for the first time, you see a shot of the gang, T.J's hat and hair colour are mixed up.
Continuity mistake: When The Library Kid is telling her story to the gang, her flashback includes a visual of her walking into the kindergarten class. The kindergarteners shown are the same kindergarteners in the current timeline, however Gretchen explains that the kindergarteners used in the flashback are now in 4th grade. (00:03:15 - 00:03:45)
Continuity mistake: When library kid sees her kindergarten class she's wearing a dress but when she runs into the library she's wearing a t-shirt and skirt.
Continuity mistake: The Library Kid says her classmates were savages. This is all well and good, except the kindergartners shown are the present day kindergartners.