At the black market, Duff Killigan is preparing to sell Dr. Drakken the Centurion Project, which he has stolen, when Kim and Ron arrive, and they escape with the Centurion Project, stuck on Kim's wrist. Back in Middleton, Ron prepares for his annual trick-or-treating with Kim, who doesn't wish to go, due to feeling that she is too old. When she hears her brothers are also not going, and that Josh Mankey will be at Monique's Halloween party, she lies and tells Ron she's going to a haunted house at the Middleton Medical Center with her parents to spare his feelings. However, when her mom overhears this, Kim impulsively lies to her too and tells her she's going out with Ron.
Unknown to Kim, both Drakken and Killigan are looking to regain the project, and having overheard parts of her conversation, head off to retrieve it. Ron is interrupted and captured by Killigan, while Drakken & Shego arrive at the haunted house, but both are surprised to not find Kim. Kim meanwhile, has learned the Centurion Project activates when its user is stressed (which she becomes when she lies/is embarrassed in front of Josh), causing the project to slowly cover her in armor.
Hearing about the danger, Kim leaves the party and battles the villains, which she easily defeats with the Centurion Project. However, her parents, Ron, and even the villains themselves, chew her out over lying, which also nearly put Ron and her family in danger, and she is grounded for a month. Josh comes over to visit, and Ron offers him the chance to come trick-or-treating with him, which he oddly accepts. Kim then asks if she can come with them next year, but is ignored.
This is chronologically the last episode of Season 1.
This episode provides examples of:
- All for Nothing: Kim tells multiple lies to avoid trick-or-treating with Ron, thinking she's too old for it, in order to attend a party that her crush Josh Mankey is also attending. In the end when her lies are exposed and she ends up grounded for a month, Josh is revealed to actually like trick-or-treating, meaning that her lying was in vain.
- Between My Legs: When the Centurion Project suit completely covers Kim's entire body and shreds her princess costume, we have a shot of Josh Mankey and Monique between her legs.
- Bullying a Dragon: Drakken, Shego, and Killigan all keep picking a fight with the Centurion-suited Kim even after it's made clear the armor can handle anything they throw at it, without Kim having to lift a finger.
- Call-Back: Kim went as a cowboy (with Ron as a ballerina) for trick-or-treating in preschool. Monique dresses as a cowgirl for the party.
- Captain Obvious: After Killigan calls Drakken a criminal for refusing to pay him for the Centurion Project, Drakken replies, "My dear fellow, I repeatedly try to Take Over the World. Of course I'm criminal!"
- Clingy MacGuffin: After retrieving the Centurion Project device, Kim finds that it's stuck around her wrist.
- Comically Missing the Point: Kim tells Ron she doesn't want to go trick-or-treating that year due to some kid calling her "ma'am" the previous year.Ron: That just means you command respect.Kim: I was dressed as a clown.Ron: Excuse me, I believe you were a hobo.
- Continuity Nod: The location where Killigan attempts to sell the Centurion Project is the black market from "Number One" (which was, ironically, Killigan's previous appearance).
- "Could Have Avoided This!" Plot: In the end, the Tweebs of all people point out this whole mess could have been avoided if Kim had just been honest about her Halloween plans with their parents and Ron, since they would've understood.
- Curse Cut Short:Bunny Kid: (to Ron) Mister, could you not do "smell my feet?" It's really lame.Ron: Hey, unicorn came to play!Bunny Kid: You're not a unicorn, you're just a horse's-
- Domino Mask: When Drakken tells Shego to "blend in" at the Possibles' Halloween party, she just adds a mask to her usual outfit, which Drakken interprets (probably correctly) as mockery:Drakken: You're just trying to annoy me, aren't you?
- Dramatic Thunder - Thunder can be heard when Kim’s parents realize she lied to them.
- Empathic Weapon: How the Centurion Project works; when its wearer is stressed in combat (or lying, in Kim's case), it creates Powered Armor to protect them.
- Even Evil Has Standards: Played for Laughs; Drakken, Shego, and Killigan are all disappointed with how Kim is lying to both Ron and her parents.Drakken: I, for one, am extremely disappointed in Kim.Shego: I know! Lying to her parents and her best friend, hmm!Killigan: She'll be working long and hard to regain my trust.
- Facepalm: Kim does one when her dad tells her he can’t figure out how to get the Centurion bracelet off and she’s stuck with it for the weekend.
- False Reassurance: Mrs. Possible tells Kim that her brothers are looking forward to drenching her in fake blood. "At least I hope it's fake," Mrs. Possible said.
- "Fawlty Towers" Plot: The basic plot of the episode, where Kim tells one lie, gets caught, and has to cover that lie up with another lie, causing her increasing amounts of grief and ultimately crashing down around her ears by the climax.
- From the Mouths of Babes: The trick-or-treater who not only nearly calls Ron a "horse's ass" but does call Killigan a "girl" for wearing a "skirt"note .
- Full-Name Ultimatum: When Kim's parents find out she lied so that she could go to a party instead of her usual trick-or-treat rounds with Ron — "Kimberly Anne Possible! Wherever you are, you are in big trouble!"
- Halloween Costume Characterization: In a Bait-and-Switch, Ron reminisces on when he and Kim went as a cowboy and a ballerina for Halloween in preschool. It’s revealed however, that Kim was the cowboy and Ron was the ballerina - fitting for their Masculine Girl, Feminine Boy dynamic.
- Halloween Episode: It's right there in the episode's title.
- Honesty Aesop: Don't lie to protect people's feelings. You can unintentionally make things worse if you do.
- Identical Stranger: A guy who looks identical to Ned appears dressed as a mummy. Unlike Ned, he is blonde.
- Man in a Kilt: Killigan has to deal with several characters thinking he’s dressed like a girl for Halloween because of his kilt.Bunny Kid: He’s dressed like a girl!Killigan: Am not!Bunny Kid: You’re wearing a skirt!Killigan: It’s a KILT!
- Match Cut: Ron’s flashback ends with Kim looking at Ron prancing around in his ballerina costume with a rather unamused expression. The scene then cuts back to Kim making the same exact face in the present day.
- Not So Above It All: Josh Mankey, of all people, excitedly joins Ron in trick-or-treating. This is after practically everyone else keeps telling Ron it’s lame.
- O.O.C. Is Serious Business: Kim lying; even her enemies are shocked that she would do so.
- Pinocchio Nose: Kim’s stress about lying to her loved ones causes the Centurion suit to take over more of her body each time.Wade: You must be more stressed out when you’re lying than when you’re fighting. Way to go, Pinocchio.
- Powered Armor: What the Centurion Project can become.
- Running Gag: People mistaking Duff for a lady, due to him wearing a kilt.
- Shout-Out: "You apparently are more stressed when you lie than when you fight. Way to go, Pinocchio!"
- Skewed Priorities: Ron was less upset that Killigan captured him than he was that it cost him his trick-or-treat time. "I'm not getting that time back!"
- Snowball Lie: Kim lies to Ron in order to get out of trick-or-treating with him so she can go to Monique’s party. However, her mom hears her tell him that she’ll be going with them instead, so she then has to tell her mom that she actually will be going with Ron. It all becomes a convoluted mess that Kim struggles to keep up with.
- Split-Screen Phone Call: When Monique calls to talk to Kim about her Halloween party.
- Strange Minds Think Alike:(Drakken is seen cruising around town in his hovercraft with a listening device, which gives out)Drakken: Stupid machine, never works when I'm roaming!(cut to Killigan in his blimp)Killigan: (regarding his radar) Foul machine, never works when I'm roaming!
- Technobabble: Wade’s description of Project Centurion, which certainly sounds impressive but doesn’t actually mean anything.Wade: Cutting-edge nanotechnology. The cybertronic circuitry is controlled by some...biometric parameters.
- Throw the Dog a Bone: Throughout the episode (like many others), Ron’s interests are dismissed as childish and lame by everyone. In the end, however, Josh Mankey gladly joins Ron in trick-or-treating, thinking it’ll be cool.
- Too Old to Trick-or-Treat: Ron prepares for his annual trick-or-treat outing with Kim. However, she doesn't want to go, feeling that she is too old. She only becomes more convinced of this when the Tweebs say they’re over “candy begging.” Even Killigan thinks Kim’s too old when he finds out about her going with Ron. Subverted when, after the truth comes out, Josh thinks Ron's trick-or-treating plans are cool and decides to join him.
- Two Men, One Dress: Ron wants Kim to go as a unicorn with him for Halloween, with one of them wearing the front half and one of them wearing the back. At least he gave her the head.
- Two-Timer Date: Kim's dilemma for the episode: go trick-or-treating with Ron, help out her family at a charity event, or see Josh Mankey at Monique's party, the last one being her choice.
- What the Hell, Hero?: Kim gets called out big time at the end for lying by both Ron and her family (who subsequently ground her for one month). Even the villains in the episode join in on the calling out while they’re being carried away.
- You Are Grounded!: Kim gets grounded at the end of the episode for one month.
