When the Janitor is flicking cotton balls, he doubles the bet after each failure from his original $5. When the situation is revisited, he owes Dr Kelso $700. However, for this debt to be possible, the number would have to be part of the sequence '5*(2^(n-1))', and it is not.
With the cotton ball flicking bets, the original bet between Dr. Kelso and the Janitor was $5. After the first miss, the Janitor first goes double or nothing.
Later in the episode, we see a ton of cotton balls lying all over the nurse's station. Assuming the Janitor kept betting $5 with Dr. Kelso, he missed 140 consecutive shots ($700 / $5 a shot) before he put another cotton ball into the jar.
Dr. Kelso only has one testicle.
In the scene where Lonnie says Carla's hair looks nice and Turk head-buts him, you can see that Turk's head doesn't really get that close to him.
When we see J.D trying on all kinds of costumes for his date with Kylie, one of them is the purple jumpsuit (which Eddie Murphy wore in "Raw") J.D buys this suit (and a matching one for Turk) in episode 3, season 4 "My New Game".
When the Janitor first pings a cotton ball into the jar in front of Dr. Kelso, he flicks it off-screen and then it drops straight down into the jar, if the ball had actually continued it's trajectory it would have overshot and missed the jar entirely.
When the quarantine defences begin locking down, Jordon slides through the door and her hat blows off, when it hits the ground it rolls through the door behind her, then the camera changes and it's moved a few feet behind her, then it changes again and it's moved AGAIN, propped up against the doorframe.
Kylie: Let's go.
J.D.: Kylie, wait. I paid Steve fifty bucks and an I.O.U. for another hundred and twenty to fake a heart attack. I just-I really wanted tonight to go well.
Kylie: Is there anything else?
Danni: Adios, assface.
J.D.: I had sex with her. A lot.
Kylie: Why are you telling me this?
J.D.: If I don't come clean now, whether it's a few weeks or months or years from now, I know it's gonna come back to haunt me and ruin us, and I don't want that.
Kylie: I'm not looking for a project.
J.D.: Yeah... I understand. It's...
Kylie: So get it together. Now let's go get some coffee.
J.D.: Now, keep an eye on the bum's vitals. I gave him enough sedative to put down a rhino.
(Elliot notices the unconscious bum)
Elliot: Wow, he is really out.
J.D.: A mild sedative fell into his juice box.
Carla: Give him a break! What if you found out Jordan had a history with somebody here?
Dr. Cox: Oh, fair enough. Uh, hey, everyone! In the brief eighteen months that Jordan and I weren't together, how many of you had your way with her?
(Just about everyone raises their hands, except J.D., who tries to look innocent.)
Dr. Cox: Bear in mind, I'm gonna need absolute honesty here or I will brain you.
(When Kylie's attention is turned, J.D. quickly sticks his hand up.)
Dr. Cox: Anyway, whoever taught Jordan that reverse cowgirl position... it's long overdue, but thank you.
Dr. Mickhead: You're welcome.
Carla: You're a freak.
Dr. Cox: Hey, baby.
Carla: Keep it together.
Dr. Cox: Do you remember that quarantine we had seven years ago? It was just you and me, all alone late at night here in the I.C.U.?
Turk: That's it.
Carla: Turk! You really had to do that?
Dr. Cox: Come on. If he wasn't such a jealous baby, it wouldn't be such a big deal.
J.D.: What the hell are you doing?
Bum: I need more cash.
J.D.: For what?
Bum: I'm puttin' DSL in my box.
J.D.: Fine! But know this: you've been nothing but a disappointment to me since the moment I ran over you.
Danni: J.D.! J.D.! Look at me! (She blows her mouth on the glass)
Kylie: Ugh! That's exactly the kind of girl my ex-boyfriend would have dated.
J.D.: I barely know her.
J.D.'s Narration: And the lies begin again.
J.D.: I certainly would never sleep with her.
J.D.'s Narration: That's it - you're stronger than this. Not another lie!
J.D.: I race motorcycles.
Carla: Okay, maybe I'm guilty of a lie of omission.
Turk: 'Cause you're a lie omitter!
Elliot: So, you just tell her the truth, she's mad at you for a little while, and then she forgives ya.
J.D.: I see what you're saying! There's no downside!
Carla: The worst first date that I ever had was with this guy who took me to this dump of a pizza parlor, right?
Turk: Yeah... you know what? Really don't wanna hear about this one. Okay!
Dr. Cox: ...And she didn't like the pizza I ordered because it had anchovies on it. You believe that?
Carla: It had anchovies.
Dr. Cox: And pineapples.
Carla: And pineapples?
Dr. Cox: And red peppers.
Carla: And green peppers.
Carla: Wait - red peppers!
Bum: I want more money.
Bum: Fifty bucks or I tell the girl.
J.D.: I don't have it!
Bum: Get it!
J.D.: Elliot, I need another doctor over here, stat!
J.D.: Gimme thirty dollars.
Elliot: I gave you twenty, I'm tapped! Ask Johnson. He's loaded.
J.D.: I need a dermatologist over here, stat!
Dr. Johnson: Oh yeah! Time to shine! What do you need? Is it a rash?
Dr. Kelso: So how much does he owe me, Barbarino?
Todd: Six hundred so far.
Janitor: Dammit, man, you cannot afford this.
Turk: You can't smoke in here.
Danni: I don't see any signs.
J.D.'s Narration: There was nothing exciting going on...
J.D.: This sucks! I need to look like a stud, and a doctor can't look like a stud unless he's saving somebody's life. I need someone to have a heart attack!
Bum: Got twenty bucks?
Dr. Kelso: I haven't eaten since yesterday. I've been starving myself because I was going to a steakhouse tonight. It was just gonna be me, a 24-ounce porterhouse, and a fistful of blood thinners.
Janitor: That's an incredibly boring story!
Doug: Smooth maneuver, hoover. You scared her off.
Ted: You were the one who was embarrassingly forward!
J.D.: So be honest - is this the worst first date you've ever been on or what?
Kylie: I don't know. I think it's kind of exciting... being in a hospital, getting to see you in action. I just wish I could be your assistant.
J.D.: Say no more. Lonnie, shirt!
J.D.: Don't make me say pants. I'll do it... Still tanning, I see.
Kylie: He's your bitch, isn't he?
Danni: Quarantinis, anyone?
Danni: Dr. Dorkian, I presume?
J.D.'s Narration: The ex-girlfriend from hell. Get out! Get out before she sprays her toxic stink all over your new relationship!
J.D.: Danni, love to stay and talk, but I'm giving Kylie here a tour of the I.C.U.
Bum: Hey. Hey, hey! You were gonna take me back to the underpass!
J.D.: After the tour! What is it with you and the underpass?
J.D.: Anyway, we only lost about a half hour. We can still make that reservation!
(He starts up the car and backs out, hitting a large box behind them.)
J.D.: Oh, there's possums everywhere!
Kylie: No, no no no. It's just a box.
(The box groans)
Kylie: A... talking box.
Carla: You know, on a first date, I could see what a guy was wearing and know exactly how far he was gonna get that night.
Elliot: Oh, me, too. And that guy's gettin' boobies.
Carla: Yeah, he is.
(J.D. takes off his sport jacket to reveal his button-up is short-sleeved.)
Elliot: Whoa! That guy's gettin' a hug at the door. Heh.
(J.D. takes off the button-up to reveal that his red tee is actually an "Electric Boogie" belly shirt.)
Elliot: And that guy is getting a fake name and a phone number with six digits.
J.D.: I know how ridiculous this looks.
Carla: I don't think you do.
J.D.'s Narration: Dr. Kelso made me realize that lies come back to haunt you - even little ones about cake.
Turk: I don't understand why Carla didn't tell me about you guys.
Dr. Cox: Maybe it's because she's really in love with me, and together we injected you with diabetes to very slowly get you out of the picture. Or maybe it's because I really liked her, but she didn't exactly feel the same way about me and I got the forehead kiss after spending ninety stinkin' dollars on theater tickets. Or maybe - and this is a huge outside maybe - maybe she knows that you're the kind of person who freaks out over irrelevant things from the past. Personally, I hope it's all three.
J.D.: Thanks, Elliot. Really. But that's a load of crap, because nobody is themselves when they start dating. Dating is just acting like you're somebody you're not until the person likes you enough so you can show 'em who you really are.
Elliot: No, it's not.
J.D.: What do you call that bra you wore for your date last week?
Elliot: Oh, the Miracle Lift Super Push-Up bra? But not everyone's as insecure as me.
J.D.: Carla, when you first started dating Turk, didn't you tell him you loved watching NBA basketball every weekend?
J.D.: And how many games have you watched since he proposed?
Carla: One. But only because that time he made me choose between watching basketball or having sex.
Dr. Kelso: The only thing I detest more than treating patients is treating patients on an empty stomach. I'm famished!
Janitor: We've been in here for eight minutes.
Turk: You dated the devil.
Turk: And you lied to me.
Carla: No, uh-uh! No. You never asked me if I dated Dr. Cox. You can ask me anything, I would never lie to you.
Turk: Do you sometimes wish I had hair?
Turk: This is a nightmare. I'm standing here living in a nightmare.
J.D.'s Narration: I could hear the pain in my best friend's voice, and I could feel how little I cared... because by the way Kylie was looking at me, I knew she thought I was sexy.
Kylie: You know something? Seeing you in your element today, you seem so...
J.D.'s Narration: Here it comes - sexy!
J.D.'s Narration: She would have said sexy if I had a mustache.
Elliot: I had this one first date where the guy took me to play paintball. All he does the whole time is shoot me in the face. After two years with that guy, I'm like, "That's enough!" You know?
Janitor: Ha ha! First dates, huh?... Someone give me seven hundred bucks.
Todd: I went out with this girl, she was like the worst first date ever. I take her for a romantic ferry ride, and for some reason I decide to take it out-
Carla: Okay. Your turn is done.
J.D.: Look, I paid this guy to fake a heart attack. He wants fifty bucks, we only have twenty.
Dr Johnson: You know, I feel like you guys just use me for my money.
J.D.: You have a trust fund! Now gimme the money!
Dr. Cox: So, Nurse Ghandirella, I need you to suction this guy, do a wet-to-dry dressing change, and, oh, what the hell, go ahead and top him off with one of your special, special sponge baths - happy ending optional, his choice, not yours.
Turk: This guy's in a coma.
Dr. Cox: Not all of him.
Turk: Baby, that's a nurse stuff, I don't have the expertise.
Carla: Turk, any idiot can be a nurse.
Turk: I know, I just think--
Carla: I knew you thought that! I knew it.
Turk: You tricked me!
Ted: Turk and Carla's wedding - we made out?
Doug: So did we.
Danni: Was it at the same time? Because I have a habit of doing that at people's weddings.
J.D.: You look ridiculous.
J.D.'s Narration: Except for that glorious mustache.
Elliot: So, Kylie looks like she's having fun.
J.D.: It's a front. She's miserable. So far the highlight of the night's been putting the possum to sleep and that's not a euphemism.
Elliot: J.D., seeing a young doctor do his job is an amazing turn-on for a girl. My dad's a doctor, and I remember how excited I was the first time I saw him work at the hospital. I mean, I didn't want to sleep with him, but there were definitely some complicated feelings. But that's totally normal for an 11-year-old, right?
Dr. Cox: Otherwise, let's bear in mind that we are short-handed - there are only four doctors here.
Turk: I counted more than that.
Dr. Cox: I'm talking legitimate doctors, turtle head. Here, Pee-Pants is a pathologist, so he doesn't count. Johnson is a dermatologist, which is Greek for "fake doctor," and please don't even get me started on you four surgeons.
Todd: There's only two of us.
Dr. Cox: You are so very useless, I counted you both twice.
Todd: Yeah you did!
Danni: SARS sucks.
Dr. Cox: Okay. You can direct any technical questions to my former sister-in-law.
Dr. Kelso: Unfortunately, by hospital policy, we have to stay locked down until the labs come back, and that's going to take several hours. So let's hang in there and not forget this is all Dr. Dorian's fault.
J.D.: Kylie, angry mob. Angry mob, Kylie.
Dr. Kelso: Mr. Donaldson hasn't been to Hong Kong in twenty years, so I bet my one remaining testicle no one has SARS.
J.D.: It's so great, because the residents are practically our slaves.
J.D.'s Narration: Aggghhh! I just said "slaves" to my new black girlfriend!
Lonnie: Are you doing this because I forgot to shave this morning?
J.D.'s Narration: Good lord! That's a one-day mustache?
Dr. Cox: She's your nightmare sister. You take her out to dinner.
Jordan: I spent the whole day with her. She stole a sweater!
Danni: So what? You're the one wearing it. Now let's go eat. I've had nothing all day except vodka and olives.
J.D.'s Narration: A hundred and twenty dollars for a stupid dead rat!?
Kylie: I think it's so sweet that you're depressed about that poor little possum.
J.D.: I'll always remember him. Little Carlton. I named him after my uncle. He had red eyes. Allergic to preserves, but he spread 'em on everything, you know?
Kylie: It's a poor little possum! We should take him to the vet!
J.D.'s Narration: It was Sophie's Choice. Either heartlessly leave the possum there to die or wrap that little guy up in my sports coat and reveal the short-sleeved nerd jersey that lurked beneath.
Danni: Didn't I go to your wedding?
Turk: Yeah, you threw up on my gram-gram.
Danni: Wanna hang out?
Dr. Cox: Depends. Does "hang out" mean "choke you"?
Raiders of the Lost Ark: When the ward is under lockdown, the music playing is similar to the Raiders theme. Additionally, as Jordan dives underneath the closing door, she grabs her hat just before it shuts, like Harrison Ford (Indiana Jones) does while escaping a tomb in the Peruvian jungle, which occurs at the beginning of the movie.