She was originally voiced by the late Lucille Bliss, and is currently voiced by Tress MacNeille.
Anastasia and her mother and sister constantly plot to ruin and torment Cinderella and have no qualms about hurting her feelings. Lady Tremaine is well aware of her daughters' harsh and cold-hearted and even violent mannerisms and can trigger Anastasia and Drizella's anger with a mere handful of casually-delivered words.
In a particularly distressing scene in the original film, as Lady Tremaine and her jealous daughters prepare to leave for the Prince's ball, Cinderella appears wearing her beautiful homemade gown. Lady Tremaine notes that Cinderella is wearing a pearl necklace that belonged to Drizella, who rejected it on the claims she was sick of the sight of it.
After Lady Tremaine casually points out to Drizella that the necklace adds a charming touch to the dress, Drizella flies into a rage and yanks the necklace from Cinderella's neck, which prompts Anastasia to realize that Cinderella is wearing her sash and the duo proceed to rip the dress about, leaving Cinderella devastated.
Anastasia and her sister attend the ball with their mother but are outshined by Cinderella in disguise. In the end, the Prince chooses Cinderella over Anastasia and Drizella and the two of them live happily ever after.
In this sequel, Anastasia acts as a major protagonist, abandoning most of her wicked ways after falling in love with the Baker. Lady Tremaine and Drizella disapprove of the relationship, due to the Baker's low status. Cinderella attempts to help the two of them be together and in the end, she succeeds, with Anastasia and the Baker falling in love.
Cinderella III: A Twist in Time
Anastasia acts as the former secondary antagonist again with Drizella, though unlike Drizella, she reforms and helps save the day against her family. Prior to this, Anastasia finds the Fairy Godmother's wand and delivers it to Lady Tremaine, who uses it to change the past and make the shoe fit Anastasia's foot instead of Cinderella, leading him to choose her instead. However, Anastasia eventually reveals their evil plot to everyone and helps stop her mother and reunite Cinderella and the Prince. She was spared by the king and forgived by everyone. She fell for the baker and also got to live in the castle with Cinderella.
Appearances in other media
House of Mouse
In the series House of Mouse, Anastasia makes several cameos, mostly sitting with Drizella and Lucifer. She is also one of the villains to take over the House of Mouse in Mickey's House of Villains.
Anastasia appears in Once Upon a Time in Wonderland as one of the two main antagonists, portrayed by Emma Rigby. She is the Red Queen of Wonderland and is not related to Cinderella, but instead has another stepsister with a parallel storyline to Cinderella's. Anastasia has a bad relationship with her mother, due to the Prince choosing her stepsister over her.
Much like Anastasia's relationship with the Baker in Disney, Anastasia the Red Queen falls in love with Will Scarlet, whom her mother does not approve of. This leads to them retreating to Wonderland, where Anastasia betrays him for power to become the Red Queen. She eventually allies with Jafar until her reformation.
Once Upon a Time
Anastasia also appears in Once Upon a Time during the seventh season. This version is indeed related to Cinderella as her stepsister, but is not initially a villainous portrayal of the character, instead of being kind and sweet to Cinderella and others. However, she becomes a member of the Coven of the Eight in the mid-season finale, implying a fall into villainy.
In Once Upon a Time, some of Anastasia's storyline aspects are given to Clorinda, while her styling is given to Tisbe.
While it has become common for Anastasia to be known as the nicer sister, in the original film she was just as cruel as Drizella.