She is voiced by Grey DeLisle in the English version of the cartoon, and by Serena Sigismondo in the Italian version of the cartoon.
Jackie has shoulder-length platinum blond hair with an aqua streak on the left side, mint green eyes, and freckles. She wears a green and white raglan shirt, a golden seashell necklace, cyan jean shorts, green and white kneesocks, and blue and white shoes.
In "Brittney's Party", she wears a yellow flower in her hair, a purple top with blue jeans, and beige boots. She also keeps her seashell necklace.
In "Sleepover", she wears a white top with shoulder straps, blue shorts with a golden seashell image on the right leg, white socks, and a golden, swirl-shaped necklace.
In "Bon Bon the Birthday Clown", she wears a sea green dress with a matching sash around her waist, her golden seashell necklace, and a red flower in her hair for her date with Marco.
Jackie is a very laid back and kind girl who is shown to enjoy and have a talent for skateboarding. She is initially unaware of Marco's crush on her until the events of "Sleepover", and she is generally cordial towards him when they interact. She has been impressed with him a few times, but sometimes displays confusion when Marco behaves awkwardly around her. On one occasion when Marco broke her skateboard, she hardly displayed any anger towards him.
In "Bon Bon the Birthday Clown", Jackie is stated to have an interest in history books and mellow music, and she admits to admiring Marco's never-give-up attitude.
Jackie Lynn Thomas is a skateboarding girl who has been Marco's crush since kindergarten.
She and Marco start dating in the season 2 episode "Bon Bon the Birthday Clown", but ended their relationship in the season 3 episode "Sophomore Slump"
- In "Freeze Day", it is shown that Jackie has known Marco since kindergarten.
- It is also shown that her name may be spelled without the "C", as seen just briefly in the background. This could be an animation error or an intentional misspelling due to Jackie's young age.
- Jackie's voice actress, Grey Griffin, also voices Queen Butterfly and Hope.
- In "Bon Bon the Birthday Clown", Jackie kisses Marco for the first time and officially becomes his girlfriend.
- Jackie is Bisexual.