Recurring
Kayla Maisonet as Lindsay, Avery's best friend. Lindsay's unique quality is that she always wears a hat, even when it is inappropriate. Lindsay often talks fast when she panics, often leading Avery to also talk fast. Except for her lack of intelligence, she has much in common with Avery. They love the same books and movies and often say the same things at the same time involuntarily, and she also dislikes Karl just like Avery. However, Avery dislikes Karl more than she does. In Avery B. Jealous, Wes, Avery's crush, asks Lindsay out on a date. Lindsay promises Avery that she will call off the date, but when they get in a fight, she decides to go out with Wes. Lindsay admits that she has always had a crush on Wes. In Avery-body Dance Now, she and Max confront Wes when he turns Avery down on an invite to the school dance after Karl tells Wes he is going with Avery.
Denyse Tontz as Nikki Ortiz, Avery's friend and Tyler's current girlfriend. She has a dog named Evita, who Stan despises because she yaps too much. Nikki moved from El Salvador and is sweet and talented. In Wingstan, she is shown to be great at whistling and art. In Avery's First Crush, Nikki accidentally reveals her confusing and mysterious secret: "My brother didn't fall. He was pushed." In Love Ty-Angle, she becomes jealous of Tyler's girlfriend and is confused about it. Nikki asks Tyler to dump Emily for her, but since he can't trust his dream girl, he chooses Emily; however, she learns about Nikki's pursuit of Tyler. This leads to Tyler being broken up with by Emily and, despite never being picked second for anything, Nikki accepts when Tyler chooses her. It is later revealed in Dog on a Catwalk that they decided to take a break because the president of El Salvador asked Nikki to stay to increase tourism with her beautiful traits.
LJ Benet as Karl Fink, Avery's frenemy. He and Avery are the smartest children in school; however, in contrast to Avery, Karl is a shameless jerk. Being very nosy, he often barges into the Jennings–James house without knocking. He also tries to find out Stan's secret in The Bone Identity. He despises Avery because when they were much younger, she stole his graham crackers at a science camp. He often has tea and snacks with Ellen, much to the discomfort of others, though they both claim that it is not weird. He once admits that he likes to send Ellen flowers under the alias of Walter Perkins. Karl has mentioned several times that his father is up on the International Space Station and talks often about his obsessive bodybuilding mother, who he says is the strongest woman in the world, though she has never been seen on the show. In Avery-body Dance Now, he teaches Avery how to dance for the school dance with Wes; however, he tells Wes that he is going to the school dance with Avery. In Karl Finds Out Stan's Secret, it is revealed that Karl has been spying on Stan and the children for a while. Now he knows that Stan can talk, but keeps it a secret.
Danielle Soibelman as Max, one of Avery and Lindsay's best friends, as shown in the second season. She is shown to be a very negative, but overall nice, person despite sporting dark clothing. She likes to act tough and says she hates everything, but she also dances with Karl at the school dance.
Peyton Meyer as Wes, Avery's crush in the second season. In Lost in Stanslation, Avery acts as his Spanish tutor; at the end, he asks her if it would be inappropriate to ask her out on a date in Spanish, but since she does not actually know the language, she answers yes in Spanish. He is very upset as he had said he wanted to ask her that even before she was his tutor. In Avery B. Jealous, Wes asks Lindsay out after being rejected by Avery, but in the end he says that he is glad that he isn't going with Lindsay as he wanted to go with Avery all along. In Avery-body Dance Now, he asks Avery to go to the school dance with him; however, when Avery seeks dance lessons from Karl, Wes becomes jealous of Karl, and when Karl tells Wes he is going with Avery, Wes goes by himself. After Lindsay and Max witness Wes' anger at Avery and Avery running out of the dance in tears, they learn of Karl's deception. Wes goes to Avery's house, where he tells her he likes her, and they return to the dance together. In The Green Eyed Monster, Stan accidentally captures a photo of Wes with another girl in the park, and Avery confronts him, which causes a temporary problem between her and Wes as he tells her he can't date a girl who doesn't trust him, but Tyler and Stan get together to convince Wes it wasn't Avery's fault and that she just has strange relatives. In Love, Lose and a Beanbag Toss, Avery notices that Wes is ignoring her; after several confrontations he finally tells her that his family is moving to another city. They both agree on a long-distance relationship through the Internet, but soon notice that it is not going to work out well. They then decide to end their relationship and try to move on.
Griffin Kunitz as Mason, Chloe's current boyfriend. According to Chloe in Stan Gets Schooled, Chloe and Mason started their relationship because Chloe came up to him, said "You're my boyfriend!" and gave him a tongue click. It is shown in Stan Has Puppies that he has twin brother named Jason.
Brighid Fleming as Heather Collins, Princess' owner and the Jennings–James' next-door neighbor who moved in with her family in Stan Falls in Love. She is shown to be spoiled, ridiculously snobby, and stuck up. She also seems to have a liking to Karl.
