The video game system that Sheen plays at the camp site looks exactly like an NES, there's even a logo that looks like the Nintendo logo on the system.
What was Sheen doing carrying a pepper grinder in his pocket?
The shape of the virus that Jimmy extracted DNA from is unique to that of a bacteriophage, which very rarely makes healthy people sick--a whole classroom's worth of people, nonetheless.
The music that played in "Aaughh!! Wilderness!!" during the chase seen between Jimmy, Carl, and Sheen and the bear was from the song "Yakety Sax" by Boots Randolph.
Before the patch absorbed into everyone's skin, Libby had already gotten the wasp sting and Cindy had the acupuncture done. But when they complained to Jimmy about the patch, they had no marks on them. When they went to school after they were cured, Libby suddenly has the wasp sting in the middle of her forehead, and Cindy had the acupuncture marks on her.
One of the toys in Carl's stomach is the duck that Hugh had in the movie - Dorkus Ducky, from the cereal Sugar Quacks.
Journey to the Center of Carl" marks the first time someone other than Jimmy says "Gotta Blast!" as Miss Fowl says "Gotta Blast!" while imitating Jimmy.
When Mrs. Vortex is treating Cindy with acupuncture, she tells her to relax, as there are only 678 more needles to go. However, when Libby says that her wasp sting really hurt, Cindy tells her to try 678 needles and then talk to her about pain. At the time Mrs. Vortex said there were 678 needles to go, Cindy already had needles in parts of her, so the total must've been higher than 678.
The viruses pictured in the stomach are much larger than the cells. In fact, they are fairly large. Real viruses are in the 20-200 nm range. That is still very small, being 2 to 20 millionths of a centimeter. The viruses pictured had a structure similar to a T-even bacteriophage, a virus that only attacks E. coli bacteria. Only T-even phages have so complex a structure. Viruses do not have mitochondrions. The mitochondrions are strictly in plant, animal, fungal and protist cells. Viruses and bacteria do not have them. The whole process of miniturization would involve either removing mass or making atoms smaller. If the atoms were made smaller without changing their mass also, then they would remain as heavy as they were. Though it would be possible if the atoms were made smaller and lighter, but that is not possible, considering it would rewrite most of the laws of the universe.
Jimmy would've been harmed in Carl's stomach acid.
Nick: (very scared, rocking back and forth) No more leeches, mama... No more leeches, mama...
Miss Fowl: Teaching is the only thing that keeps me alive... (simulating) How do clouds create rain, Carl? (pretending to be Carl) Ummm... well, when the clouds get very sad, they cry. (as herself) No, Carl. Jimmy? (pretending to be Jimmy) Water vapor condenses on a particle called a condensation nucleus.. Gotta blast! (as herself) Very good, Jimmy. Oh, I miss them all so much... except Sheen!
Jimmy: Look, there's Carl's brain!
Sheen: Where? I don't see it! Is it behind that walnut on a stick?
Jimmy: Um, actually...
(trying to distract the germs)
Jimmy: Sheen, start crying!
Sheen: How am I supposed to cry right now? I don't cry; I'm a man!
Jimmy: Pretend that UltraLord just got canceled!
Sheen: (his eye twitches) NOOOOOOOOO!!! (starts crying) Why is the world so cruel?!
Jimmy (while trying to fly out of Carl): Well, we could always pull a Pinocchio.
Sheen: We're gonna turn into puppets?! Cool!
Jimmy: No, but if we had something to make Carl sneeze like the whale in Pinocchio, we'd get out.
Hugh: Don't forget I was an Acorn Lad! I remember everything I ever learned - like the song we used to sing! (singing) We are the Acorn Lads, something, something, the Acorn Lads....
Carl: Here's today's homework, Jimmy! Gee, you look really sick....
Sheen: Yeah! You look like you have berry berry fever! Have you been eating any berries that were foaming at the mouth?
Hugh: (singing) Your hip bone's connected to your ... bone next to it. That bone's connected to your ... uh, Jimmy, what's the bone on your knee?
Miss Fowl: Please give a nice, warm, friendly welcome to Yentil Marmelstein!
Yentil: Hi. I--(sneezes) Oh, sorry. I have a cold.
Libby: Keep her away from us!
Sheen: (crossing his fingers) Unclean! Unclean!
Carl: Santuary! Santuary!
Jimmy: Run for your lives!
(the kids run out of the room, screaming)
Miss Fowl: I think they like you!
Hugh: Behold, bear! I am man! The pointy tip of the food chain! Gaze upon my opposable thumbs and tremble! (to Jimmy, Carl, and Sheen) Yeah, they hate it when you mention the thumbs.
This episode aired during a week of Brand New Nicktoons Everynight, including Hey Arnold, Rugrats, Rocket Power, & The Fairly Odd Parents.
"Journey to the Center of Carl" can be seen on the DVD Sea of Trouble.
"Journey to the Center of Carl" was originally supposed to air with "Broadcast Blues." "Aaughh!! Wilderness!!" was originally going to be a full 30-minute episode.
"We are the acorn lads" song
Seriously just me thinking this and maybe others. But it think that song is kind of a spoof of Queen's "We are the Champions".
Movie reference: Fantastic Voyage
The plot of this episode is similar to the plot of the movie and books "Fantastic Voyage" where people shrink to microscopic size in order to gain something important from someone.
Nick: No more leeches, Mama...no more leeches, Mama...no more leeches, Mama...
This is referring to how leeches were used, and still are used, to treat for medicinal purposes. For more information on leeches used for medicine, click here.
Background: Kirby Poster In the scene where Mr. Wheezer is in the big plastic bubble, you will see a poster that says Poofy-Dee on it. This is probably a spoof of the Nintendo character Kirby.
When Jimmy pulls out his Neutronic camp-in-a-box, an NES, Nintendo's first US system, falls beside the TV/fireplace.
Sheen: Here's Johnny!
Sheen's second impression is spoofed from a line in Stephen King's movie The Shining. The main character, Jack, is driven mad by a ghost haunting a hotel. He is often quoted as saying "Heeere's Johnny!"
Sheen: That's All Folks!
Porky Pig said, stuttering, "Abdmena, abdmena, that's all folks!" at the end of almost every Warner Bros. cartoon.
Title: "Aaughh!! Wilderness!!"
This title was probably taken from Eugene O'Neill's play Ah, Wilderness! Ironically, a 1993 Simpsons episode did a similar pun on the phrase on the title of an Itchy and Scratchy cartoon:Aaah!!! Wilderness!!!"
Sheen: You dirty rat!
Sheen's third impression is of James Cagney.
Sheen: You're supposed to play with the toys in the Silly Meals, not eat 'em!
"Silly Meals" is a take-off of McDonald's "Happy Meals."
Title: Journey to the Center of Carl
The title is taken from the movie Journey to the Center of the Earth.