Stewart Walldinger is a young boy whom Hazelnut Middle School classmate Nicky Little had a crush on. Despite Pepper Ann Pearson's attempts to separate them, due to her perceived notion that Stewart was not cool enough to hang out at an eighth grade party, they fell in love and, to Pepper Ann's surprise, revealed that Stewart was well liked by the eighth graders due to his intellect. Since then, he has been accepted into Pepper Ann's friend group and remained close and loyal to Nicky due to their shared down-to-earth activities.
Over the course of the series, Stewart and Nicky's relationship is tested not just by external forces, but also their own interests such as Stewart's love of slot car racing and Nicky's love of playing the viola, which they ironically despise of the other. Stewart had a habit of getting ignored whenever a situation not pertaining to him gets out of control. He will offer help and advice whenever he is needed though sometimes this will blow up in his face, or not be heard, just like with Nicky.
In "The Finale", it is established that in the series' version of 2013, Stewart and Nicky's relationship only lasted two years. As an adult, Stewart has become desperate to win Nicky back, yet no one remembers who he is. He meets up with Gwen Mezzrow and ends up going out with her, but does not remember her from their middle school days.
Stewart is, by all accounts, a really nice and congenial person. Soft-spoken and kind hearted, he is more than willing to share his interests and help those around him. While he rarely shows it, he can get angered or annoyed at the many antics of Pepper Ann, but will usually revert back to a calm demeanor. Pepper Ann considered him a "creep", which he was not happy to hear, however in "The Finale", it is established that he is indeed somewhat clingy and possibly nostalgic for his past, showing that he has a lot of emotional baggage.
Stewart is a tall slender Caucasian boy with curly black hair and rectangular glasses. He wears an orange turtle neck sweater, yellow/green plaid pants, a belt with an oval buckle featuring an "S", yellow socks and black and white dress shoes.
- Stewart is of Italian descent and even speaks the language.
- Stewart has two voice actors: Luke Perry, who voiced him in seasons 2 and 3, as well as one episode in season 5 ("Two's Company"), and Cam Clarke, in season 4 and the rest of season 5, making him the only character to have been recast.