Intrigued by Wanda Maximoff's ability to alter reality, she infiltrates the Hex and, unaffected by its properties, adopts the persona of "Agnes," a nosy neighbor.

She subtly manipulates situations to raise suspicion about newcomer Geraldine (Monica Rambeau) and later controls the mind of local actor Ralph Bohner to impersonate Maximoff's deceased brother, Pietro.

At a recording studio tied to Lorna Wu, a famous witch musician and Wu-Gulliver's late mother, Vidal approaches Harkness and they flirtatiously discuss betraying the group.

Attacked by Wu-Gulliver's generational curse, Harkness concludes that Wu's renowned cover of "The Ballad of the Witches' Road" functions as a protection spell.

Harkness emerges in her backyard in Westview, still without magical powers, where Death confronts her for rejecting her affection and failing to deliver Billy Maximoff.

In an alternate version of the 1930s, Agatha Harkness discovers the Celestial Tiamut within Earth and devises a plan to steal his energy through a ritual requiring vast resources.

To achieve this, she collaborates with Howard Stark, starring in his production to access the necessary tools, and eventually convinces co-star Kingo to join her plan to stop the Emergence.

At their film's premiere, Harkness and Kingo speak about their vision to inspire humanity, whereas the latter worries that other Celestials will not leave the news of Arishem's death unanswered.

[2] She trained the Scarlet Witch / Wanda Maximoff in the art of magic[3] and was revealed to be the mother of the warlock Nicholas Scratch and the grandmother of the Salem's Seven.

Kathryn Hahn's casting in the role of "Agnes", Wanda and Vision's neighbor, was announced at Disney's biennial D23 Expo convention in August 2019.

[7] Head writer Jac Schaeffer explained the decision to introduce Agatha Harkness was made due to her Marvel Comics connection to Wanda Maximoff's stories.

Following the conclusion of her character's story in WandaVision, Hahn signed an overall deal with Marvel Studios to reprise her role in multiple projects.

[12] The miniseries was released on Disney+ from September 18 to October 30 and told the story of Agatha Harkness and Maximoff's reincarnated son Billy assembling a coven to go down the Witches' Road in search of power.

Hahn imagined Harkness "really enjoyed sticking around and being in these sitcoms", and portrayed her relationship with Wanda Maximoff as a witch who has been "flying around for a couple of centuries without a coven" and "would love to have a friend for a second".

[16] When continuing the character's story in Agatha All Along, showrunner Jac Schaeffer and Hahn deemed it important to maintain her "acerbic, sarcastic, self-involved" demeanor while placing her in a position where she begrudgingly needs a community.

Schaeffer maintained that Harkness would "understand the permanence of his [Nicholas'] death" and subvert the villain trope of being motivated by a desire to resurrect a loved one.

Schaeffer described their dynamic as reflecting Harkness' attraction to power and her desire to be challenged, serving as a metaphor for her complex and enduring relationship with the concept of death.

She wielded dark magic and was able to absorb life force energy and power from others, as seen in the trial flashback in WandaVision and her centuries-long Witches' Road con in Agatha All Along.

Harkness casts binding runes that disable other witches' magic within her controlled space, and creates illusions to deceive others, such as transforming herself into a 1950s, black-and-white look to blend in with Maximoff's Hex upon arriving in Westview.

She demonstrates the ability to alter the form of objects, transforming a cicada into a bird in "Previously On", and takes control of Ralph Bohner's mind in "Breaking the Fourth Wall", forcing him to play the part of Pietro Maximoff.

[23][24][25] Agatha Harkness in the MCU has had a distinctly villainous depiction compared to her comic book counterpart, who is an ally to the Fantastic Four and a long-term mentor to Wanda Maximoff.

[26] Originally intended to align with her Marvel Comics role as a magical teacher, Jac Schaeffer pivoted the character to a villain to serve as a foil for Maximoff.

[9] By the end of Agatha All Along, the character references her comics version more extensively as she transforms into a ghost and guides Maximoff's son, Billy, on his journey.

[15] Portrayed by Kathryn Hahn, Harkness' physical appearance in the MCU is aged-down in comparison to the comics prior to her revival and the restoration of her youthful look.

Jean Henegan of Pop Culture Maniacs celebrated the Harkness-centric miniseries for "letting her [Harkness] simply be the morally bankrupt character we loved from WandaVision – just with much more personally at stake this time around.

"[47] CBR's Joshua M. Patton concluded that avoiding a redemption arc for Harkness allowed her to become "more human and sympathetic" without compromising her villainy, which he described as "the best choice for a villain-focused series like this.

The website's commentary reads, "Agatha's cruel power was made clear through Hahn's acting choices, like the way her eyes lit up just before her old coven turned on Wanda, or the pleasure she took in revealing that the Hex couldn't actually be fixed with a new spell.

[59] For her work on Agatha All Along's fifth episode, "Darkest Hour / Wake Thy Power", Hahn was a featured performer once again, this time as an honorable mention for the week ending October 12, 2024.

Rebecca Iannucci commented that "Kathryn Hahn has one of the most formidable acting ranges in the business" and commended her for "her comedy chops [...] and her subtle dramatic skill".

[60] The publication went on to include Hahn among their 20 finalists for Performer of the Year in December 2024, with R. I. praising her "delicate moments: her hints of genuine longing for Vidal; the glimpses of grief over her son's death; and her surprising — ill-advised, even!