Spinelli is one of the six kids in the Recess gang and T.J's best friend. She is a gruff, tough tomboy and hates whenever she's referred to by her first name, due to it being associated with the local snobs of the school, the "Ashleys", with whom she wants nothing to do with. She often tries to result to physical violence, with one of her friends usually stopping her. Despite being very violent at times, she is very kind and warmhearted, and roots for the underdog. She and Vince are considered to be T.J.'s "right hand men" in the show, and it has been revealed many times that she has a crush on T.J. as well. She is also an accomplished artist, as seen in the episode, "Spinelli's Masterpiece". In the episode "Parents' Night", it's shown that she has very embarrassing parents, as they arrive at the school pronouncing her friends' names wrong and also show her friends pictures of her as a baby, we also learn that they are secret agents. She also dislikes her mother's preference of her to have more "girly" traits. Because of this, she often looks up to her teacher, Miss Grotke, as a mother figure to her. In "Weekend at Muriel's", it is revealed that her parents and her maternal grandmother, Aggie, are family friends of Ms. Finster. In fact, Spinelli's grandmother used to have fun with Ms. Finster in Guam back in the 1950s.
- She is the opposite of Mikey in many ways. While Mikey is kind, good-hearted, sweet, gentle, peaceful and poetic, Spinelli is tough, aggressive, angry, tomboyish and somewhat rebellious.
- Mikey is interested in poetry, singing, art, philosophy and is more interested in arts and culture, while Spinelli is interested in wrestling, fighting, sports and physical activity. While Mikey's interests are spiritual, Spinelli's interests are more physical and manly. Also Mikey's interests are considered more suitable for females, while Spinelli's interests are considered more suitable for males.
- While Mikey is sensitive, tolerant and forgiving, Spinelli is rough, less tolerant and less forgiving.
- She seems to search out female role-models other than her own mother throughout the series, admiring, looking up to, and finding solace in the advice and confidence of Miss Finster, Miss Grotke and Madame Pavlova, revealing a much more sensitive side.
- She is an accomplished artist. During the episode Spinelli's Masterpiece she creates an expansive piece of artwork across the blacktop which Gretchen describes as resembling "one of those giant aboriginal petroglyphs that can only be viewed from the sky." Had it survived the incident with the hose, she would have been offered a lucrative grant from Collette Découpage.
- Spinelli's birth date is never revealed, but Miss Grotke mentions in the episode "Mama's Girl" that she is a Libra, meaning that she was born between the month and dates of September 24th and October 23rd. And since she is at the age of 9 and the show was made in the year 1997, she was likely born in the year 1988.
- Throughout the show's run, various hints have been dropped that Spinelli has feelings for T.J. There are also suggestions that T.J. may well share these feelings.
- Spinelli is the only member of the Recess Gang to be voiced by an adult (though in a few foreign dubs, she's voiced by a kid). Also, like Gretchen and Vince, she is one of the only members of the main six to keep her voice actress for the entire series run, including movies and the Lilo & Stitch crossover.
- Spinelli was based on a girl whom Paul Germain and Joe Ansolabehere knew from college.
- In the Fillmore! episode, "Codename: Electric Haircut", Spinelli makes a cameo among the students in the lunchroom, along with fellow Disney character Kim Possible.
- Spinelli is mentioned in an episode of Lloyd in Space another show that Paul Germain and Joe Ansolabehere have made.
- In the Portuguese dub, Spinelli's first name is changed to Patricia.
- Spinelli is the only member of the Recess Gang who isn't drawn with nostrils.
- According to the official website for the series, her favorite colors are black and blue.
- She was named after her Great Aunt Ashley, who was the first woman to win the Iditarod (in reality, the first woman to win the Iditarod was Libby Riddles in 1985).
- Her first name is Ashley. She admits that she actually does like her first name, but the only reason she doesn't want to be called Ashley is because she doesn't want to be part of The Ashleys.
- She gets angry really easy.
- Spinelli's middle name is quite likely a nod to Annette Funicello.