Abigail "Abby" Archer unravels mysteries so disgusting that no adult will touch them. She loves everything gross and slimy – nothing grosses her out. Abby likes to test her limits to see if there is something so gross, so slimy, and so disgusting, that it will make even her, the Queen of Squeam, turn green. So far, although she has gagged at gross sights on a few rare occasions, like in "The Slim Slime Man" and "Go Fish", nothing has succeeded in making her hurl. The only time she has thrown up was in the episode "Yack Attack", when she unknowingly drank contaminated water and fell sick. As a Grossologist, she gets covered in slop a lot, but being dirty has yet to affect her trademark ponytail.
She holds deep dislike for villains like Lance Boil, and Paige, her rival at school. On the field, she is a competent fighter, with impressive aim with her goop shooter, great hand-to-hand skills and quick reflexes, performing acrobatic manoeuvres without a second thought. She is more athletic than her younger brother Ty, She has a fear of leeches, as shown in the episode "Vein Drain". She shares ownership of a kitten called Hairball with her brother Ty. Her speaking accent could be described as slightly English.
Abby has a multifaceted personality. She is very intelligent and kind, but can also be fashionable at times, particularly towards her brother. While protective of the people she is close to, she can also be more demanding towards them. She is frank, rarely hesitating to speak her mind, and is considered the perfectionist student in class. She sympathizes with the weak and is ready to confront those who abuse like others, hence her likes for people like jocks, Paige, and the villains she fights. As the only girl in the Bureau of Grossology, Abby sometimes sees things that Lab Rat and Ty fail to notice, which also occasionally highlights the differences between boys and girls. This was particularly evident in "The Greatest Race Ever Crawled", where Abby's annoyance with Lab Rat and Ty demonstrated a small but marked differnce between her and the males on the team. Another personality trait that she possesses, which seems somewhat linked with the fact that she is a girl, is her sweet but sometimes seemingly excessive and inexplicable fascination with cuteness, which has on several occasions drawn mild annoyance and slightly sardonic remarks from her brother. She is a determined and strong-willded, never once allowing Pagie's teasing to depress her, although it nonetheless gets on her nerves.</p>
Ty Archer – When it comes to Ty, Abby is the typical older sister. She cares about her brother very much, but she also can get very annoyed with him, which sometimes results in her admonishing him, but can also lead to huge fights. One example was in the episode "Club Parasites", where Abby got fed up with Ty's constant teasing about her head lice. While she finds her brother's jokes annoying from time to time, she enjoys poking fun at him just as much as he enjoys teasing her, making jokes about things ranging from his flatulence to his nervousness in his budding love life. She has quite a lot in common with her brother, including her sense of humor and her love of all things gross. Abby is also known to be a typical caring sister, even though Ty teases her a lot. Also, she is protective of her brother, when villains try to attack Ty, Abby is always in action. One example was in the episode "The Insider" when Lance Boil entered Ty's body, Abby went in after him.</p>
Paige Logan – Abby's arch rival never fails to try to get her down. Abby and Paige tend to loathe each other and give snide remarks whenever someone comes by. They are consistently at the mall, like theirs over Ty’s decorations for a school dance,and even the boy they like. As the School President and the archetypal prissy rich girl, Paige hangs out with her two friends by shopping and flaunting her family's wealth, but Abby hates Paige.</p>Chester/Kid Rot – In season one, Abby got to know Chester, a new kid at school who was picked on frequently by other kids. Abby showed a lot of concern for him, constantly tried to help him and has been kind to him. She had a crush on him since her actions could have been her personality more than anything else. Nevertheless, all significant feelings of care towards him ended when she realized that the parasite within him had fully taken over and given him a new persona, Kid Rot, which she came to hate.
Rudy – Rudy is a blond-haired boy at school whose name was introduced in "Hairless Whispers", Season 2. He is also Abby's crush, and it appears that the liking is mutual. This is shown at the end of the Valentine's Day episode, "Pucker Up", where Rudy walks by to greet Abby while she is reading a card that seems to have been sent by him. While Abby is rarely seen interacting with him, it seems that she dreams of spending some time with him, once even setting her virtual training program in the Gag Lab to simulate a dance with him, as part of her resolution to "enjoy being young". Rudy is also seen in the first episode, "Queen for a Day", where he is helping Abby string the bee up during the Spring Festival.</p>
Abby has long brunette/red hair that is tied into a long ponytail that reaches her feet and has blue eyes. She has violet shirt and black leggings under her purple mini skirt and purple shoes. She is always seen with Ty but is rarely alone. She wears a yellow slimesuit. In Hairless Whispers, Abby's hair turns blonde, and Frederick Follicle gets rid of Abby's hair.