Cassandra never knew her parents and was adopted and raised as the daughter of Corona's Captain of the Guards. She is a skilled fighter who dreams of joining the royal guard, though she currently — and contently — serves as Rapunzel's lady-in-waiting and closest confidante, alongside the princess' pet chameleon Pascal. Her role generally requires that she assist Rapunzel in any means necessary. She also played an instrumental role in the return of Rapunzel's 70-feet of magic, golden hair.
Cassandra is described as being "tough-as-nails", a fitting description for someone who wishes to join the royal guard. She is snarky, sarcastic and has a somewhat dry sense of humor. Despite this, she is extremely supportive and protective toward Rapunzel, her polar opposite—so much so, that she openly holds animosity for Eugene, believing him to be selfish and undeserving of Rapunzel's love and friendship. One of the reasons for this belief is because she feels that Eugene puts his own desires before Rapunzel's, which she expresses to Eugene. In the series, however, their relationship gradually becomes less hostile, and slightly more playful as the two spend more time together. In "Fitzherbert P.I.", Cassandra genuinely admired Eugene's determination to become a royal guard, and actively assisted him in proving his worth to her father. It was later shown that Eugene's quirkiness had started to warm up to Cassandra, who found amusement in his excitement to school the guards as head of a training class.
Aside from her no-nonsense persona, Cassandra is also a free-spirit, not unlike Rapunzel. Though she has a more cynical way of going about life, Cassandra also finds joy in adventure, living life to the fullest, and experiencing new things. This is most notably seen during "Wind in My Hair", where Cassandra is seen enjoying herself almost as much as Rapunzel.
Although loyal to King Frederic and Queen Arianna, Cassandra is willing to break their rules (and risk her job) for the sake of Rapunzel's happiness; this is seen when Cassandra offered to take Rapunzel beyond the kingdom's wall to explore some of the outside world and escape the pressures of royalty. Doing so required much stealth and cunning, traits Cassandra revealed herself to have that night.
In "Rapunzel's Enemy" and "Fitzherbert P.I.", it is shown that Cassandra respects Corona's history a great deal, and considers it an esteemed honor to uphold the kingdom's traditions.
In "Challenge of the Brave", it is revealed that Cassandra has some insecurities about how she is seen just as a girl/handmaiden instead of the strong, skilled, and capable female who deserves as much respect as anyone in the royal guard. These insecurities caused her to take out her frustrations on Rapunzel, who joined the Challenge of the Brave to have fun, not understanding why it was so important to Cassandra.
Cassandra is a pale-skinned young woman around Rapunzel's age with dark pink lips, hazel eyes and black bob-cut hair with gray highlights.
Her signature outfit is a grayish-brown shirt, black leather gloves, a dark brown belt with a purse and a dagger on it, dark brown-and-red striped leggings and brown boots.
Cassandra is first seen waiting for Rapunzel's return from a ride with Eugene at Corona's village gates. From there, Cassandra takes Rapunzel to attend to the various duties of a princess, specifically in preparation for her upcoming coronation ceremony to officially crown her as heir to the throne. Rapunzel laments her feelings of stress of the pressures of royalty overwhelm her. Cassandra believes the princess should take a break regardless of what her father wishes, but Rapunzel refuses to do so. Later at a dinner event, Cassandra sits with Pascal, while Rapunzel sits with her parents, and Eugene sits at the children's table (an arrangement made by Cassandra, who was in charge of seating). Eugene takes the time to propose to Rapunzel, but due to her fears of being bound to life in the castle, Rapunzel rejects and leaves. Seeing the princess upset angers Cassandra, who glares at Eugene.
That night, Rapunzel agrees to relieve her built-up tension by following Cassandra beyond Corona's border wall to explore the outside world for the night. Cassandra gears up for the adventure, providing Rapunzel with a hooded cloak and the two sneak their way out through a hidden passageway. They journey through the night forest, until Cassandra takes Rapunzel to a specific spot where the golden flower that saved Queen Arianna and the yet-to-be-born Rapunzel was grown. Suddenly, a blast of magic hits the two that causes Rapunzel's magic, golden hair to return.
The two return to the castle where Cassandra tries desperately to cut the hair. Like the rocks, it's unbreakable. When Eugene arrives, an anxious Cassandra urges Rapunzel not to tell him about the hair, fearing he'll tell the king and queen, which would cost Cassandra her job. He discovers regardless, but the three agree to keep it a secret from everyone else, including Rapunzel's parents. What Eugene still doesn't know, however, is how the hair came to be again. Cassandra refuses to tell him, and when confronted about her behavior towards him, Eugene discovers that his unintentional selfishness in regards to Rapunzel is partially to blame.
At Rapunzel's coronation, the hair is kept hidden beneath a wig, only to be revealed when she needs to utilize it as a weapon to fight off a band of thieves. While Rapunzel and Eugene fight off the goons, Cassandra takes on their leader Lady Caine. Caine is defeated and arrested for her crimes, though Rapunzel is reprimanded by King Frederic for the hair but Cassandra's part in restoring it was left out by Rapunzel.
Cassandra returns in the series as a major character, taking place immediately after the events of Tangled: Before Ever After.
In the premiere episode, "What the Hair?!", a week has passed since the return of Rapunzel's hair, and Cassandra is dead set on ensuring her involvement remains a secret. Rapunzel feels increasingly guilty over keeping Eugene in the dark, but Cassandra reminds her that if the secret is revealed, she would lose her job and be sent to a convent as punishment. After Cassandra subsequently proves Eugene's inability to keep a secret, Rapunzel agrees, though not without apprehension. By the end of the day, Rapunzel finally reveals the truth to Eugene, though he promises to keep it between them for Cassandra's sake.
In "Rapunzel's Enemy", Cassandra is tasked with caring for the gopher for the 500th Good Will Gopher Grab tournament, something she and the rest of Corona take seriously, with the exception of Eugene. Eugene nearly ruins Cassandra's work when he accidentally feeds the gopher dim-berries instead of bim-berries, the former in which makes rodents go berserk.
In "Fitzherbert P.I.", Cassandra condescendingly questions what it is Eugene does for a living, prompting him to seek out a job. He eventually sets his sights on joining the royal guard, and Cassandra attends his training sessions alongside Maximus to watch. She is surprised by how well Eugene accomplishes the drills, but is unamused by her father's attempts to sabotage his training to prevent him from joining. Eugene takes note of this and nearly gives up, knowing the Captain will surely sabotage his final training day, thus tarnishing all of his hard work. Cassandra visits Eugene and encourages him to "fight fire with fire", by simply countering the Captain's schemes with a few of his own. The final day of training arrives, and Eugene takes Cassandra's advice, earning his spot on the guard. After accidentally allowing a thief to escape, however, Eugene is fired. He later reports a theft to the Captain, but the latter refuses to believe him. Cassandra trusts Eugene's instincts, and offers her help, though she playfully claims that if he's wrong, she'll relish in his embarrassment. The two ride their horses to the docks alongside Shorty the Pub Thug, but only Eugene makes it to the ship the thief has boarded. He and Maximus successfully apprehend the criminal, thus earning the Captain's respect, though not enough to regain his position on the guard. The Captain instead assigns Eugene to a pivotal teaching duty for the guards, something Eugene finds great amusement in, which in turn amuses Cassandra.
In "Challenge of the Brave", Cassandra enters a challenge that tests the strength of its competitors to determine who is the mightiest warriors in all the seven kingdoms. She sees it as an opportunity to prove her worth (as she receives ridicule for her role as Rapunzel's lady-in-waiting) as she wishes to someday join the royal guard. However, Rapunzel enters the tournament as well, and this inadvertently humiliates Cassandra and sparks a rivalry between herself and the princess. As Rapunzel gracefully rises above the competition, Cassandra becomes increasingly spiteful and riddled with envy, driving her to attempt to sabotage Rapunzel's chances of winning the final match. During said match, Rapunzel notices Cassandra's aggression toward her and stops the fight to talk things out. She apologizes to Cassandra for failing to realize how importance the challenge was to the latter, and confesses that she entered as a means to spend time with her. The two reconcile and finishes their match with their only remaining opponent Wreck Marauder. Unfortunately, Cassandra loses as well, earning Rapunzel the trophy. Rapunzel believes Cassandra deserves it more so, and bestows the prize onto her. As Cassandra receives the praise she's desired, she and Rapunzel walk off together with their friendship restored.
- Interestingly, Cassandra's will to protect Rapunzel at all costs is also quite damaging, specifically with the relationship Rapunzel shares with Eugene. Because of Cassandra's distrust toward Eugene, the former actively advises Rapunzel to keep secrets from him, which in turn cripples the amount of trust shared between the two; though Cassandra blames Eugene for failing to address Rapunzel's personal struggles, it is impossible for him to do so if Rapunzel refuses to be honest with him. Though Rapunzel is at fault for choosing to keep secrets, Cassandra is also at fault for encouraging the princess' will to do so. This was addressed in "What the Hair?!".
- The name Cassandra means "praise of men" in Greek.