Buffy the Vampire Slayer/Recap/S1/E11 Out of Mind, Out of Sight

"Looking in the mirror day after day and seeing nothing there? It's an overrated pleasure."

A wallflower classmate becomes invisible from lack of attention. And psychotic.

Air Vent Passageway: Marcie has a hideout in the suspended ceiling.
Batter Up
Brick Joke: Willow and Xander tell Snyder that Marcie's victim is going to sue the school. Later when Harmony gets her ankle broken by Marcie, Synder examines it.

Harmony: Ow!
Snyder: (looking alarmed) Don't sue.

Deadly Gas: Marcie locks the Scoobies in a basement and opens a gas valve.
Ghostly Chill: The absence of this tells the Scoobies they're not dealing with a poltergeist.
Glasgow Grin: Marcie intends to inflict this on Cordelia, amongst other assorted facial mutilations.
Hidden Depths: Cordelia. This is also the first episode in which she starts to get closer to the Scoobies.
Hilarious in Hindsight: When Buffy mentions Marcie used to play the flute Willow dismisses this. Then came American Pie...
If You Can Read This...: A Spy School textbook on infiltrating a cult compound to assassinate its leader is readable in DVD format, and consists of the lyrics to "Happiness is a Warm Gun" by The Beatles.
- Well given Charles Manson's liking for The Beatles...
Incredibly Lame Pun:

Giles: I've never actually heard of anyone attacked by a lone baseball bat before.
Xander: Maybe it's a vampire bat. (everyone stares at him) ...I'm alone on that one, huh?

Insane Equals Violent: Marcie. Good lord, Marcie.
It's All About Me: Cordelia again.

Cordelia: People who think their problems are so huge craze me. Like this time I sort of ran over this girl on her bike. It was the most traumatizing event of my life, and she's trying to make it about her leg! Like my pain meant nothing.

- Later on:

Cordelia: Somebody is after me! They just tried to kill Ms. Miller! Uh, she was helping me with my homework. And Mitch! And Harmony?! This is all about me! Me, me, me!
Xander: Wow! For once she's right!

It Sucks to Be the Chosen One: Buffy pines for the pre-Slayer days when she was popular.
Lame Comeback: Cordelia is giving out chocolates to drum up votes.

Cordelia: Here's a chocolate... (realises it's Buffy) Oh, I don't think I need the loony-fringe vote.
Buffy: Well, I don't even like chocolates! (to herself) Okay, that was the lamest comeback of our times.

Laughing Mad
Men in Black
Monochrome Past: Marcie's flashbacks of her non-interactions with Sunnydale students.
Monster of the Week
Noodle Incident: Buffy feels left out when Xander and Willow start laughing over a past Cordelia incident.

Xander: Cordelia, man, she does love titles!
Willow: (laughing hysterically) Oh, God! Remember in sixth grade with the field trip?
Xander: Right! Right! The guy with the antlers on his belt!
Willow: Be my Deputy!
Xander: And remember the-the hat?
Willow: Oh God! The hat!
Buffy: Gee, it's fun that we're speaking in tongues.

Not So Different: Spoofed.

Cordelia: Buffy, I, uh, I, I know we've had our differences, with you being so weird and all, and hanging out with these total losers... Well, anyway, despite all of that, I know that you share this feeling that we have for each other, deep down...
Willow: Nausea?

Oblivious Mockery: Played straight with Xander mocking Cordelia's May Queen obsession, when Buffy used to be one. Played for Laughs with Cordelia who's so used to insulting the Scoobies she even does it when asking them for help.
Power Perversion Potential: Xander Thinking Of The Potential of being invisible. And protecting girls' locker rooms.
Quantum Mechanics Can Do Anything: With a little help from the Hellmouth anyway.
So Beautiful It's a Curse: Buffy and Cordelia share a rare moment of bonding over this.
Spy School: Marcie gets sent to one.
Stock Quotes: The two FBI men talk in official clichese.

FBI 1: We're not at liberty to discuss that.
FBI 2: It would be best for you to forget this whole incident.
Buffy: Do you know that you guys are very creepy?
FBI 2: Thank you for your help.

Vertical Kidnapping: Marcie on Cordelia.
We Need a Distraction: Principal Snyder intercepts Buffy as she goes to check out the locker room where Mitch was attacked. Willow and Xander distract him by claiming Mitch's dad is going to sue the school. Later Marcie draws the Scoobies away from Buffy and Cordelia with a tape recording of her playing the flute.
With Great Power Comes Great Insanity: Marcie becomes insane after she becomes invisible.
What Happened to the Mouse?: While government projects involving the supernatural will return in a big way in season 4, the project involving training invisible people as assassins is never mentioned again.
Your Eyes Can Deceive You: Buffy is unable to land a punch on Marcie until she shuts her eyes and just listens.
You're Insane!

Buffy: There's one thing I didn't factor into all of this. You're a raving loony!

Your Mind Makes It Real: Inverted: Other people's perception of Marcie as not worth noticing made her invisible.