Gretchen is the smartest of the main kids in the show. In a few episodes, it's shown that she's smarter than almost everyone else in town, as shown in "A Genius Among Us", where it's established that she's smarter than most of the teachers at school. Gretchen is also somewhat of a "big sister" to the main six, usually to T.J. and Gus. She often argues with Vince, but appears to be very close to him as well, hinting that she may have feelings for him (and vice versa). Out of all the members of the main six, Gretchen seems closer to Spinelli than she does to any of the boys.
Although she is very smart, she can also be sweet, and a bit naïve (mostly due to her young age). At times, she can easily fall for most of the crazy stories told on the playground, such as the outcomes of the Stinky Peterson fortune teller in "Gus's Fortune". She's also very unathletic, as shown in "Gretchen and the Secret of Yo," but is shown to be very skilled at yo-yos.
She is one of the few kids on the playground to get along with one of the Ashleys, Ashley A., as seen in "Outcast Ashley", where Ashley A. is kicked out of the clique for forgetting a tradition in the group. When looking for friends, she decides to hang out with Gretchen. The two become friends for a while, until Ashley A. is welcomed back into the clique. Their friendship is seldom seen again.
One device Gretchen is usually seen with is her Gallileao, a small, handheld computer with a talking frog mascot.
- She, Gus and Mikey are the half of the main six to be only children--TJ has an older sister, and Vince and Spinelli each have an older brother.
- Her parents appear to be geniuses as well, so it's implied that her brains come from them.
- In the original pilot from 1996 (which would be re-made into the first episode), she had a slightly different appearance, such as her being given black hair, slightly larger buckteeth, and the blue part of her dress was white with green dots.
- Ten years after she debuted, another Gretchen, from Phineas and Ferb, was introduced, having very similar features to her.