Annie is the main character of BrainPOP Jr, along with Moby. She, Tim, and Ben are the only people who can understand Moby. Annie has a sister named Mia who talks on the phone too much. Her best friend is Becca and she is in Mr. P.'s class.

It has been strongly hinted that Annie is Mexican as her dog's name is Sr. Maurices and she sometimes refers to her father as "Papi".

Annie is a very cheerful and optimistic girl who always smiles, even when things don't go as planned or when Moby does something that others might find annoying or weird. 

Mostly, Annie wears a blue and yellow shirt, blue shorts, red glasses, three red rubber bands (two on her wrists and one on her neck), and gray shoes

During winter times, she wore a pink and blue beanie cap, a light-pink sweater, a pink and blue scarf, pink and blue mittens, purple jeans, and black boots (Hibernation and Forests), red boots (Seasons), or dark grey shoes (Winter).