Fifth graders have noses, fourth graders don't.
After Stan says that Timmy is covered, the next scene shows the kids with open mouths, as if just then they had finished yellling, "YEAH!!!"
The fourth-grade classroom looks like some chemistry rooms you see in high school, with the sinks against the wall.
Ms. Choksondik writes her name with her right hand, but the next word, "Life," with her left. In the next scene "Life" is gone.
There are various toys from "Starvin Marvin in Space" in the nerds' basement: a Marklar doll above one of the computer monitors, a figurine of the space junker on another, Marvin's ship hanging against a wall. Other items: a poster of the alien first seen in "Spooky Fish," and a poster of Xena --- "Lena".
When Timmy crashes through the chalkboard the top of the board stays straight, and the projector screen doesn't budge. Also, the pieces of wall Timmy takes out fall clear of the resulting hole. Seconds later, though, the screen is on the floor as the class sees Timmy make a right in the distance. No other debris is on the floor, and the left side of the board bends down a few inches. When the class rushes out after Timmy, the screen is back above the board, but tilted, and large slabs of wall have somehow made it back inside the classroom.
The nerds say that the system malfunctions if the chair STOPS, but Stan changes that to "malfunctions if the speed drops below 5 mph," which is a reference to Speed, in which a bus is supposed to stay above 50 mph or explode. The attempt to disarm the attached bomb with the aid of a dolly also comes from Speed.
Mr. Mackey doesn't say "m'kay" as much, and his voice shakes enough to match Butters' own stammer.
When the SWAT team member is dropped down to get Timmy, a cleared driveway and walkway are shown, but they lead nowhere. There's no garage or house attached to them.
Nerd #1 said there are 72 episodes --- and his friend said 73 --- before they fought and his friend moved out. Now he says there are 73 episodes while claiming his friend says 72.
Actually, the nerds were both wrong, there are 79 episodes of the Original Star Trek, The Menagerie was ONE episode.
The first side view of Chef
Why didn't Garrison use this line himself when he was the kids' teacher: "Present them"?
1200 --- address of Nerd #2's mother.
"The Menagerie" was a 2-parter that counts as one episode! --- Under that rule, SP episodes 113 and 202 count as one episode, as do episodes 307, 308, and 309 --- The Meteor Shower, as well as episodes 410 and 411.
Kenny appears in class after he dies, when the new time machine is activated.
Now that the boys are in fourth grade, I wouldn't be surprised if Trey and Matt get more of their ideas from One Saturday Morning's Recess, which is all about life in the fourth grade.
"Charade you are" is from Pink Floyd's "Pigs (Three Different Ones)." Cartman has used it before in episode 307 - "Cat Orgy".
"HAUNT ME NO LONGER!" is a reference to the Ghost of Christmas Past, in which the Ghost showed Scrooge a Christmas from his childhood in Charles Dickens' A Christmas Carol.
The scene where Mr. Garrison confronts Ms. Choksondik and says she'll be afraid comes from this bit of Star Wars: The Empire Strikes Back in which Yoda doubts Luke resolve and stamina:
YODA: He is too old. Yes, too old to begin the training.|
LUKE: But I've learned so much.
YODA: (sighs) Will he finish what he begins?
LUKE: I won't fail you - I'm not afraid.
YODA: (turns slowly toward him) Oh, you will be. You will be.
When Timmy comes back from the past there are stickers on his wheelchair that say Enola Gay, RAF and ??? Platoon.
By the end of the episode, Ms. Choksondik's lazy eye is gone.