Ash is an anthropomorphic porcupine. She has light brown fur with dark brown and white quills, with 5 quills next to her ears on each side of her face. She also has blue eyes, dark brown eyebrows, and a black nose. She appears to be wearing black mascara and lipstick, as well as dark brown eye shadow. She wears a light grey long sleeved shirt under her black and grey striped mid-sleeved shirt, which has two quills pinned through the front along with 3 pins: a bow-tie shaped green pin, a circle shaped yellow pin, and a circled shaped white pin with a yellow circle . She also wears a red, white and black checkered skirt with blue jeans underneath and dark blue and white lace up sneakers. During rehearsals, Ash wears a sparkly purple dress that went down to her feet, with frilly white layers underneath, a purple belt with a bow in the middle, and matching shoes, due to Buster Moon wanting to make her a "pop star princess". During her performance of "Set It All Free", she wears this dress, but she has cut up the bottom so that it is now above knee length, and she has also removed the bow from the middle. She wears this along with a red leather jacket, red stripped leggings, and black lace up boots. At the beginning of the performance, she wears Becky's red heart-shaped sunglasses, which she left in Ash's apartment when Ash kicked her and Lance out, and she throws them into the crowd after she begins performing. She also wears sparkly blue eyeshadow with this outfit.
Along with being able to sing, Ash also plays an electric guitar. Her guitar through most of the movie is red and white, with a green star sticker and what appears to be scribbles in yellow and white marker. However, the guitar she uses during her performance is black and white. She also has the ability to write songs, as she writes her own original song, "Set It All Free" for her performance, which was inspired by her getting over Lance cheating on her.
Truly a rocker at her heart, Ash's passion for playing rock music causes conflict between her and her boyfriend Lance, causing her feelings for him to blind her to his massive ego. In her introduction scene, she and Lance fail to land a gig at a restaurant, and afterwards Lance tells her that he's the lead singer and she's the backup vocals, and Ash apologizes for "getting carried away". While boarding the train, flyers for Buster's singing competition get stuck to Ash and Lance's quills. Ash takes one off of Lance, who had accidentally boarded the train without her. She runs after him showing him the flyer. The two perform at the auditions, but Buster only wants Ash, whom he describes as "loud and horrible but shows promise", and not Lance. Despite leaving with Lance after this, her yearning to make a name for herself and for Lance as true rock stars leads to her deciding to accept her earned place in Buster's singing competition even though Lance didn't make the cut. She tells Lance that she's doing this for them, but Lance believes she's just "selling out".
As a rocker and a teenager, she has her pride and a rebellious streak displayed by her sarcastic wit and a passive-aggressive defiance towards Buster's attempts to make her perform as a "pop star princess", suggesting she sing what Ash calls "cheesy pop" songs such as "Call Me Maybe", with Buster saying that the song is "made for her" due to being a teenage girl, and wear a sparkly purple dress on stage, which disagrees with her own ambition to to be a rocker in her own right. Later on, at her apartment, she and Lance laugh at the songs Buster picked for her. Ash says she was considering writing her own song, but Lance scoffs at this, saying to just do what Buster says so that they can win the money, and that writing songs isn't easy, despite him making look easy.
Ash returns to her apartment one night after rehearsals, and she sees Lance singing Jack White's "Love Interruption" with another female porcupine. The two almost share a kiss before Ash interrupts questioning what is going on, to which the girl responds by introducing herself as Becky. Shocked and angry, Ash kicks both of them out. Lance blames Ash for this, saying she was never around anymore, and Ash says she was doing it for them. Ash then slams the door on them, right after Becky attempts to tell her that she left her sunglasses inside, and she is left heartbroken. This affects her emotionally during her next rehearsal, where she attempts to sing "Call Me Maybe" while wearing the dress Buster picked out for her, but midway through she breaks down crying. Buster, oblivious to her being cheated on, asks if she's crying over having to wear the dress, which makes her cry more and shoot out her quills. Backstage, she is cheered up by Rosita and Gunter, with them saying she's too good for him and Rosita offering her gum or candy from her purse.
Ash begins to get over Lance by writing her own song called "Set It All Free". She lets Buster hear it during rehearsals, and he is very impressed and tells her she should perform it. But despite this, Ash, after leaving the site of the destroyed Moon Theater, looks upset when she sees Lance and Becky performing at the same restaurant she and Lance tried to get a gig at before, causing her to run off. However, alongside the rest of the performers, Ash showed determination in performing and does not care about the prize money or the fact that Moon lied to them about how much money was being offered, and they all help fix the stage to perform on. Ash, who has altered her performance outfit to fit her style, performs "Set It All Free", finally showing the world her passion and spirit. Her performance also draw the intention of Becky and Lance, who are watching it on TV. Becky turns off the TV, saying she isn't that good. Lance agrees with Becky as she leaves the room, but once she's gone he quickly turns the TV back on, looking very impressed. Despite her prickly performance, with her unintentionally shooting her quills everywhere during the guitar solo, she is given a thunderous applause and Buster calls her "a genuine rockstar". She is also seen cheering on the other performers, and at the end of the movie she attends the grand reopening of Moon Theater.
Ash is a prickly teenage porcupine with a punk rock attitude. She auditions for the competition with her egotistical, unsupportive jerk of a boyfriend who eventually cheats on her with Becky, unable to see just how much he is holding her back. In rehearsals, her rebellious nature continually puts her at odds with Buster, who envisions her as a pop star princess whereas Ash wants to write her own authentic rock songs that reflect her unique style.
↑8 July 2016: Vikram Murthi of IndieWire: "Ash (Scarlett Johansson), a crested porcupine in an alt-rock band with her boyfriend." 21 December 2016: Sophie Gilbert of The Atlantic: "Is that Scarlett Johansson playing a crested porcupine punk-rocker in an emotionally abusive relationship?"