Air-Vent Passageway: Inversion; Kumar breaks into a police station where Harold is being held to bust him out. And then subverted when Kumar drops through the vent onto the floor. Thankfully he made a decoy call so the station's empty.
Ambiguously Gay: The Jews (they are referred to as such), Rosenberg and Goldstein (who think the same of Harold and Kumar).
As Himself: Neil Patrick Harris, though it's a subversion as he specifically requested to be credited "as Neil Patrick Harris" instead of "as Himself", so that people didn't think he was actually a drug-sniffing, car-stealing womanizer.
He also claimed to have had sex with Whoopie Goldberg's stand-in while filming Clara's Heart at age 14.
Asian and Nerdy: Harold's co-workers cites this as justification for tricking Harold into doing his work.
Zigzagged with Harold. He's an uptight neat-freak who lets bullies from his office and neighborhood walk all over him. But he's also a stoner and an expert at beer-pong. He later ends up standing up to his bullies and screwing them over magnificently.
Subverted by Cindy Kim and her East Asian Club. They appear to be straight-laced nerds, but turn out to be drug-using party animals.
Bilingual Bonus: The movie poster in Harold's dream has the tag line "There is a pinche puto in all of us". "Pinche puto" would probably be best translated as "fucking pussy".
Black Is Bigger in Bed: Harold gets locked up in jail with a philosophical black man, who is resigned to his fate.
Harold: I don't understand how you can be so calm about all this.
Tarik: Look at me. I'm fat, black, can't dance, and I have two gay fathers. People have been messin' with me my whole life. I learned a long time ago that there's no sense gettin' all riled up every time a bunch of idiots give you a hard time. In the end, the universe tends to unfold as it should. Plus, I have a really large penis. That keeps me happy.
Bread, Eggs, Milk, Squick: "If you boys'd like to go on inside, get yourself something to drink, worship, fuck my wife, watch TV... anything you want!"
Butt Monkey: Harold. Exploited at work because of his ethnicity, has parking spaces stolen from him by extreme sports enthusiasts, his best friend uses his scissors for manscaping, he gets attacked by a raccoon, Neil Patrick Harris steals his car, he gets arrested for jaywalking (well, admittedly he also unintentionally punched the cop in the face), his laptop gets destroyed, he gets clotheslined by a tree branch while riding a cheetah, and on top of all of that, he's completely unable to talk to the girl he has a crush on. Harold isn't just the Butt Monkey; he's distinctly headed into woobie territory.
The crazy guy in the bushes compliments Kumar's "manscaping", which was mentioned near the beginning of the movie.
The dorky pot dealer that our heroes encounter at Princeton somehow ends up clad only in his underwear in the Muckleburg police station, along with Harold.
Chekhov's Gun: The split-second news report about a cheetah that escaped from the zoo.
Corrupt Cop: The Cherry Hill PD, hoo boy. They even respond to a call about a shooting (phoned in by Kumar so he can sneak into the police department and break out Harold), and arrest the nearest black man they can find, who was asleep in his home.
This turns out to be Shooting themselves in the foot when the guy turns out to be a high priced lawyer who, after being on the receiving end of overwhelming evidence of police brutality is able to have all the cops arrested.
Food Porn: The White Castle commercial that sends Harold and Kumar on their quest. It even includes sleazy-sounding porn music. There's also the Burger Shack drive-thru guy's description of White Castle burgers.
Funny Character, Boring Actor: John Cho and Kal Penn have both said their real-life personalities are more or less the reverse of their characters'.
Gilligan Cut: Immediately after Kumar insists Harold doesn't need to go to the hospital, we cut to him sitting in a hospital waiting room.
I've Come Too Far: When Harold gets in a police chase after stealing the skateboarders' car.
Harold: I'm not going back to jail, man. We've come too far.
Jerk Ass: The cops/extreme sports guys. Also, Harold's co-workers, Billy and J.D.
John Barleycorn And Friends: When Kumar is trying to liberate Harold from jail he is distracted by a giant bag of weed at the police station. Kumar immediately forgets about Harold and has an elaborate Dream Sequence where he falls in love with the anthropomorphized bag of weed—then makes love to said anthropomorphized bag of weed—then marries the bag of weed—then is stuck in a miserable squabbling marriage with the bag of weed.
The Load: Kumar is responsble for just about everything that goes wrong over the course of the night, other than the scene where Harold slams on the gas pedal because he's scared of talking to Maria.
Harold: This whole night is your fault!
Manly Tears: What happens when Harold and Kumar actually made it to White Castle and feasted on those tiny, delicious burgers.
Market-Based Title: Known as Harold and Kumar Get the Munchies outside of the US and Canada, because White Castle operates solely within the US, and it can be presumed that most Canadians are familiar with the franchise as well.
And only in the Northeastern and Midwestern US, at that. This left viewers in the South and the West Coast confused, as they didn't know what White Castle was.
Strangely enough, it was screened as Harold and Kumar Go To White Castle in Singapore, the Philippines, Australia, Belgium and Canada, all of which do not have a single WC restaurant (White Castle's management seems to not want to do international franchises).
Actually, White Castle has a line of frozen foods featuring their signature sliders available in grocers and vending machines since 1987. Many people probably didn't know it was an actual restaurant at the time.
No Fourth Wall: The DVD menu for the first film, where both characters comment on the options available as well as how long the viewer takes to make a selection.
Odd Couple: Harold is the neat freak, Kumar is the slob.
Offscreen Teleportation: When our titular heroes want to cross a street at a crosswalk. Kumar convinces Harold to jaywalk, and Harold checks both directions, to find the road clear on both sides for miles. Then he steps off the sidewalk and a cop car instantly pulls up from just off-screen. Cue Kumar trying to ignore Harold's Death Glare.
P.O.V. Sequel: As noted below, the actors playing the main characters were Funny Foreigner characters in other gross-out comedies and the movie is sort of a perspective shift to focus on them; Harold's coworkers are a parody of the Jerk AssDesignated Heroes of most of these films and amusingly, all of their adventures happen offscreen. Similarly, the two have a pair of even nerdier (and Jewish) friends, Rosenberg and Goldstein who also have adventures off-screen, alluding to the play Rosencrantz and Guildenstern Are Dead which is a famous example of this.
Rant Inducing Slight / "The Reason You Suck" Speech: Both Harold and Kumar. Kumar gets his first when an asshole cop gives Harold a ticket for jaywalking after putting one foot down off the curb; Harold's comes when he runs into his co-workers at the White Castle, catching them lying about an "important business meeting" as an excuse to make Harold do all their work.
Repeat Cut: When Harold loses it right after Neil Patrick Harris steals his car.
Rock Bottom: Immediately after complaining that he doesn't know how much more he can take, Harold gets attacked by a raccoon that snuck into the car.
But there isn't one in Cherry Hill. The closest is 1 1/2 hours away (there are a couple of Chick-Fil-As though).
Not to mention that the real Cherry Hill is a very suburban area—it's 20 minutes down a major highway from Philadelphianote Also, see this map◊ on Joisey. It's in the "Happy White Families" in the southwestern section, right next to Collingswood.—it is nowhere near as rural as depicted in the film.
There is, however, a White Castle in New Brunswick (still open).
The way Freakshow and his wife talk about Jesus and church would suggest they are from a low Protestant church. Thus they probably wouldn't have many pictures and statuettes of Jesus or Mary.
A Simple Plan: Two guys want to go to a fast food restaurant; what could be simpler? Apparently, a lot.
Spit Take: Harold after Freakshow's wife asks if they're going to fuck her.
The Stoner: Almost every character is this, from the titular characters. Even the studious Asians.
Ugly Guy, Hot Wife: Freakshow, who is covered in boils (some of which have pus squirting out of them), is married to a rather good-looking woman (played by Malin Akerman (Granted, this is before she gained that bit of weight)). She cites his beautiful singing voice as the reason she fell in love with him.
Walking the Earth: The fate of Neil Patrick Harris, who is going "wherever God takes me".
"Well Done, Son" Guy: Kumar isn't interested in being a doctor like his father is, despite having perfect MCATs. He even uses his medical textbooks as paper to make joints. He has an epiphany at the end of the first film and decides to give it a shot anyway.
What the Hell, Hero?: Neil Patrick Harris attempts to avert this at the end of the first movie by approaching Harold and Kumar, apologising for his role in the previous night's events, and offering to pay for their breakfast. They then launch into this trope anyway, leaving him to irritably point out that he's aware of the dick move he pulled, hence the apology-and-offer-to-buy-their-breakfast.
Also $200 for Harold's car. He made some "love stains" in the back.