In 2008, AOL named her the twentieth greatest witch in television history.   Selena Gomez, who portrays Alex, is one of the only two cast members to appear in every single episode of the series; the only other cast member to do so is David Henrie, who portrays Justin Russo. The character has also appeared in The Suite Life on Deck episode, Double Crossed.
Alex debuts in the pilot episode of Wizards of Waverly Place, " Crazy 10-Minute Sale ", asking for permission from her father to attend a sale at a popular clothing store, "Suburban Outfitters" (a parody of the popular clothing brand Urban Outfitters), to upstage her rival since pre-school, Gigi. She cannot attend the sale as she has wizardry class, but decides to clone herself so that she can go to the sale and convince her father that she was at wizardry class. However, this plan falls through when her clone is unable to actually speak, and instead barks like a dog due to a mistake while performing the spell.
Throughout the rest of the first season are similar magical mishaps, most of which are intended to improve things, but typically end up backfiring and causing her to revert them. Alex attends Tribeca Preparatory High School throughout nearly all of the show, a fictional school whose real location is the Salk School of Science. During the first season, Alex also attends WizTech, a fictional wizardry school which she attends once during the summer. Alex is often seen at her family's restaurant, the Waverly Sub Station, a fictional diner whose image is that of the bottom floor of the Bayard-Condict Building, on Bleecker Street.
Alex also has a relationship with another student named Riley, which ends quickly after he witnesses her eating large amounts of chocolate, but begins again when she convinces him that she is a good luck charm for their school's baseball team. They finally go on a date during the third to last episode, where Alex shows herself to get jealous too easily, which cause the two to break up. Alex brings life to a mannequin which she pretends to be in a relationship with in order to make Riley jealous, which causes Riley to go back to Alex, only to be replaced with another boy the following season.
The second season continues with a myriad of spells and magic gone awry, the first of which is her joining an academic game at her school called the Quiz Bowl and wearing a pair of pants known as "Smarty Pants" that grant her infinite knowledge. She wears the pants for too long and ends up having skeleton legs, which are fixed towards the end. Another love interest of Alex's, Dean Moriarty, also makes his debut appearance in this episode, as a new student who is forced to help set up the Quiz Bowl.
Alex's infatuation with Dean is revealed to her nemesis, Gigi, after she steals Alex's magical diary and finds that Alex's " knight in shining armor " is Dean. Alex reveals this to everyone, including Dean, in order to avoid giving Gigi any sort of satisfaction from doing it herself. The two confess their love for one another during a race which Dean is involved in, and they begin their relationship.
During their relationship, Alex gets involved with another boy from WizTech, Ronald Longcape, Jr., after he is forced to leave WizTech due to a "plastic ball infestation". Ronald, after becoming infatuated with Alex himself, shapeshifts into Dean in order to "end" Alex's relationship with them. This causes Alex to start a relationship with Ronald, as it appears to her as her only option. She agrees to go to WizTech with him, where she realizes that Ronald has kidnapped Dean and put him in a block of jelly. Alex realizes that she truly loves Dean, and leaves Ronald. However, the two break up shortly after, then again in Dean's dream, after Alex uses a spell to get into his head.
During the second season, Alex reveals her and her family's wizardry to Harper during her birthday, after feeling guilty about keeping secrets from her, making her one of three mortals on the show known to have discovered the existence of wizards.
Characterization and themes
Alex, although a bit rude to others at times, is shown throughout the show to be a good person at heart. Los Angeles Times described Gomez's portrayal of her as "sweet and sassy, with a lovely elastic face and great comic timing".  DVDizzy's Kelvin Cedeno writes that, "Alex is a character that could, and should, be off-putting in her narrow-mindedness and egotism. In spite of this, Selena Gomez manages to be likable and approachable in the role.  "
Alex is usually portrayed as inconsiderate of the feelings of those around her. The A.V. Club's Marah Eaken writes, "Alex...is pretty dark. She's dry, lazy, and kind of a jerk, sometimes."  Alex is often shown to act aloof and indifferent to things, but she later reveals while under a "truth spell" that she uses her indifference as a defense mechanism to "hide [her] desire to really be liked". 
Alex often uses magic to solve her problems, which frequently ends up causing more problems than she began with. DVDizzy claimed that Alex was "cocky, self-assured, and constantly relies on magic to bail her out of mishaps".  Alex underachieves when it comes to high school, however, she excels greatly at art. She is also shown to be only semi-literate, when it is revealed that she has never fully read a book or a menu.
Alex is the middle child and the only female of the Russo family. She often argues and insults her older brother, Justin, though it is later revealed that she does so because she admires him and wishes to be like him. The fact that her parents seem to favor Justin in most cases also engenders hostility and jealousy toward her brother. Alex and Justin act as foils, as the two are near- polar opposites ; Justin is responsible and fair in judgment, though easily insecure at Alex's great magical feats. She feels insecure when seeing Justin accomplish much with his hard work and responsibility. She is shown not to be the most apt student at both "wizarding" and high school, failing her Spanish midterm, her wizardry exam, and relying on the use of magic to pass several assignments.
Despite her flaws, Alex has numerous instances of generosity, loyalty, and compassion. She shows deep care for her best friend Harper, even going as far as to reveal to her her wizardry in " Harper Knows " out of guilt for lying. Alex is shown to hate "fake people" and silent films.