"Allison" (played by Ally Sheedy) is first introduced in the beginning, stepping out the back seat of a gray sedan. She goes to the front window, as if to look in, but the car drives by her. She then begins walking towards the school. Allison is the last out of the Breakfast Club members to enter the library.
She heads all the way to the back, and faces the opposite direction. When Vice Principal Vernon walks in, for the most part, she ignores him. When he sets the paper down in front of her, she just glares at him, yet says nothing. When Principal Vernon leaves, Allison barely notices. Allison begins chewing on her nails loudly, and all of them turn to watch her. Bender looks at her for a moment before saying, "If you keep eating your hand, you won't be hungry for lunch."
He then replies, "I've seen you before, ya know." When Bender and all of them are talking / arguing, Allison is the only one not to join in on the first conversation. She smiles slightly when Brian makes the comment of Andy wearing tights for wrestling. Once Bender takes the screw out of the door, she's also watching him with the others. Principal Vernon walks in once more, interrogating them about why it's closed. When he asks, "Who closed that door?" again, Allison squeals and bangs her head against the desk. Bender looks perplexed then says to Vernon, "She doesn't talk." Once Principal Vernon leaves, she lifts her hood slightly to see what he was trying to do to keep the door open.
When the door is closed, Allison passes the time first by wrapping a string around her index finger, to make the tip purple. She then passes it by drawing a picture of a bridge with her pen. She works on it and appears to be a very good artist. She then begins scratching her head wildly, so her dandruff would fall on the paper to make it look like it was snowing. Then Allison carefully brings her head down onto her hands, watching the others with blood-shot eyes. She then closes her eyes and falls asleep.
Allison, along with the others, raises her hand when Principal Vernon asks who needs to use the lavatory.
After they all begin whistling, Allison joins in for one slight part, before quickly shutting her mouth. She is picked along with Andy to get the soft drinks in the teachers lounge. Principal Vernon keeps snapping at her to get up, in which she does and slings her bag across her shoulder.
When walking with Andy to get the drinks, he asks, "What's your poison?" She doesn't respond, and once he gives up, she replies with, "Vodka." He then asks when she drinks, and she answers, "Whenever." At his last question, "How much?" she says, "Tons". Andy asks her if that's why she's here today, and she says no. He then states why is she, and she retorts, "Why are you?" They glare before Andy replies how his father and wrestling coach believe it'd be good for him. She doesn't believe him, telling him to tell her why he's really in here. He says forget it, and the two return to silence.
Bender chucks her a Cola, and without even looking, she catches it. She appears to be staring at the back of an album sleeve. When opening her lunch, she disdainfully throws the meat over her shoulder, in which it lands on the statue. She then takes two sugar sticks and pours them across the two pieces of bread, now and then going and gulping in the falling sugar. Once done with them, she sticks both of them into her coke. She then proceeds to place cereal on the sandwich, pounding it in. The others now watch her, and she brings up her sandwich, biting into it. She notices the others staring, but ignores them. When Bender is showing how life is at his house, she looks very concerned. After Bender climbs up the stairs, she watches him, before returning to staring at Andy, Brian, and Claire.
Allison follows the others outside the library. She is calmly walking behind them all. Once Bender gets his weed, Brian blinks at her, clearly shocked. He asks her, "Do you approve of this?" before he walks after them. Allison then quickly steals Bender's lock.
When all of them first begin running, she stays standing, only to follow them after they go in the other direction. She appears to agree with Bender when he says they have to go to the cafeteria, but when the others disagree and follow Andy's lead, she waits for him. The two then look at each other for a long time before reluctantly following the others.
When Bender is under the table, and everyone makes noise to protect his hiding spot, Allison also begins to make noises to protect Bender from getting caught by Principal Vernon. She is also the only one who doesn't smoke Bender's weed. She watches as Andy soon follows the others, realizing he does everything everybody else does, seeming very upset.
Allison answers Brian's question when he asks Andy if he knows what his middle name is. She also states his height, weight, and security code. When Andy asks how she knows all this, she states how she stole his wallet. Allison chucks it at him after he demands it back. When Brian calls her a thief, she says how she's not. She says how there's nothing to steal but two bucks and a nudity picture. She calls it perverted and seems disgruntled by it.
Allison asks if they want to see what's in her bag, and when they both say no, she seems upset, but soon dumps it out anyway. She has clothes, tampons, and other various objects in the bag, as well as a comb. When they ask if she always carries this around, Allison says they never know when she might need to break. She could run away to the ocean, or the mountains, or Israel, or Africa, or Afghanistan. She calls her home-life 'un-satisfying', and when Brian tells Andy to get in on this, Andy says everyone's homelife is unsatisfying. Brian whispers to Andy how hers might go a bit more beyond theirs. Allison snaps for them to forget it and 'There's no deal sport-o'. Andy challenges she either carries that much crap around in her back because she is actually considering running away, or she wants others to believe she is. She then gets up and says hotly, 'Eat shit' to Andy. Andy soon gets up to follow her.
Allison is doubled over on a desk full of books, crying silently. When Andy asks if she wants to talk, she tells him to go away. When Andy begins to walk away, she tells him, "You have problems!" He replies with, "Oh, I have problems!" She replies by telling him he does what everyone else does and asks him too, making that a problem. Andy responds with at least he didn't dump it out on a couch and share it with others. In a much softer, kinder tone, Andy then asks what's wrong. Andy keeps saying, "Is it bad? Real bad?" He then says, "Parents?" Allison, with tears in her eyes, says "Yeah". He asks what they do, and after a moment of hesitation, she says "They ignore me." The scene ends with Andy nodding, repeating "Yeah."
When they are all sitting in a circle, Allison is sitting between two chairs. When Andy is done saying what he would do for a million dollars, Allison says how she'd do anything sexual, and she wouldn't need to be paid. Claire rolls her eyes, stating she's lying. She also remarks how she's done a lot of sexual things except for a few things that are illegal, calling herself a nymphomaniac. She told her shrink this, and after Andy asks what he did once you said it, she says, "He nailed me". She says she didn't think it could be constitute as rape since she paid him. She also says how after the first few times, but is interrupted by Claire. Claire is disgusted by her, and Allison asks if Claire ever did it. She compares sex to a "double-edged sword". If you say no, you're a prude, and if you say yes you're a slut. Allison then later comments, "Or maybe she's a tease". This manages to get Claire to admit she's a virgin. Allison then say's she's never done it either, and that she is not a nymphomaniac; she is a compulsive liar. Claire calls her a bitch, and how she tricked her. Andy defends her, saying how Claire's just upset because Allison got her to admit something she didn't want to. Allison abruptly says how she would do it, and that it is ok if you love that person. Allison also answers for Andy when Claire asks what's his problem. She states how he cannot think for himself. Andy agrees, explaining why he got in there. Allison watches him with sympathy when he exclaims how he hates his father.
After Brian and bender argue,she breaks the silence by saying how she can write with her toes, and can also eat and brush her teeth, she can play heart and soul on the piano, all with her toes. Allison also defends Claire when Bender mocks her, saying how he promised he wouldn't laugh. When talking if they will be like their parents. Allison looks at Bender and says "It's unavoidable." when he looks back at her, they share a moment and she says "it just happens." She continues to look at bender and says "when you grow up, your heart dies." When Bender says who cares, she replies, "I care." She appears to be on the verge of tears. When talking about what would happen on Monday, she asked Claire what she would do if she walked up to her, and says "The same exact thing.", referring to ignoring her and laughing about it with her friends. Bender gets angry and defends Allison by shouting at Claire, "YOU ARE A BITCH!" Claire calls bender a hypocrite and asked what he would do if one of them walked up to him, and Allison laughs when Claire asked if he would even consider taking Allison to one of his heavy metal vomit parties. Brian says he guesses Allison and him are just better people than them. when he asked Allison what she would do, she simply states she "doesn't have any friends." but wouldn't do that to them if she did..
Later, Allison reveals how she got into detention. She did nothing, she "didn't have anything better to do". When they all laugh, she joins in.
Allison is first dancing with the statue, before going off to throw each fist up and down. Allison is tossing her hands like the backstroke at one point while dancing. Her and Bender are then onto of a desk, moving in the same direction while sliding with their feet. Her and Claire are then both shaking on the desk. The dancing scene ends with Allison ducking lower to the ground, until she just huddles there, not moving.
Allison nods her head along with Andy, giving permission to Brian to write the letter from all of them. Allison is taken away by Claire, who gives her a makeover. She puts a headband in her hair to pull it from her eyes, revealing her face. She also puts eyeliner on and gets rid of the black 'shit' under her eyes. She retorts by saying she "likes that black shit." When Allison walks out of the room, Andy looks at her in awe. She is wearing a white shirt in place of the black sweater she had on the rest of the time, and when Brian mouths 'cool!', she gives him a smile and responds with a thanks. When Andy asks her what happened, she says, "Why? Claire did it!" Andy says how she looks different, and how he can see her face. Allison asks if that's a good or bad thing, and Andy responds with 'Good'. The scene ends with both of them smiling at each other.
When they all walk out together, she walks with Andy down the stairs and outside, has his blue sweatshirt around her shoulders. Andy pulls her into a kiss, and the two kiss, until they pull apart. Andy is dumbstruck, watching her, and she rips a patch off from his jacket. He continues to stand there, watching her, slightly pulling on her as she backs away to her car, still watching him. You can see Andy turn when he gets into his car to watch Allison. Allison, in the letter, says, "And a basket-case." Allison Reynolds: The "Basket-Case"