When Arnold first sees the box and reads the attached letter, there are strings on the box but afterwards, the strings are gone.
In the episode "Monkeyman!", when Arnold says "What do you say?" to Monkeyman, his mouth doesn't move.
While Monkeyman talks almost every sentence, he adds a random "Monkeyman" into the sentence.
(after she discover a pay phone was near Helga and Harold)
Helga: (to Harold) So how much money do you got?
(Harold shows Helga two quarters in his hand) Enough for one call each. Hello, Mom! It's me, Helga! I'm stuck at the chocolate factory with a moron. The school bus left us here and we don't have any way to get back. Oh, please pick up, Miriam.
(Helga hangs up the phone)
Harold: (dials the pay phone) Hello? Mommy, it's me, Harold.
Worker at Restaurant: I never heard of you! Don't call me again!
Harold: (hangs up phone) Dialed the wrong number.
Helga: Just brilliant. You don't even know you're own phone number.
Helga: Everything that happened today was your fault. You can't do anything right! Take the bus for example. Why do you think we missed it, Harold? Oh, let's see, hmm... maybe was it be because you were too busy eating twice your bodyweight in chocolate, num-nums! Oh, how about this one? Let's take the subway, I think it goes to Lincoln. Oh wait, no it doesn't, it goes straight to the bowels of the underworld!! Population homicidal, toothless, midget clowns!! I know, let's steal their bike, they won't mind. Now, you'd think that would be enough to fill any moron's day, but you're not just any moron, are you, Harold? You're the king!! Your day's just getting started. So, because of your amazing curiosity about the world around us, you pulled the plug out of the bottom of our getaway boat!!! You idiot.
Helga: (to Sheena's Uncle Earl) Hey Mister, wake up!
Sheena's Uncle Earl: What? Who goes there?
Helga: Can you give us a ride into town?
Harold: There some crazy midget clowns that want to kill us!
Sheena's Uncle Earl: Midget clowns eh? Arr!
Harold: Hey, look. The subway. We're saved!
Helga: Yeah, great idea, genius. Only one little problem -- it costs money to take the subway, and we don't have any.
Harold: Then we'll just jump the gate. No one ever gets caught. Come on! (gets stuck on the turn-style entrance)
Cop: Hey! You two kids! Come back here!
(Helga pushes Harold through, while they both run into the moving subway, eluding the cop)
Harold: (relieved) Oh! (sighs) That was close. Oh, I think I'm going to be sick!
Helga: "No one ever gets caught."
Harold: We're all alone! We'll starve to death!
Helga: Get real, porky! You just ate half your weight in chocolate.
In "Buses, Bikes and Subways", the music for Jolly Olly Man's ice cream truck plays when Helga and Harold are near the circus tents.
Character Debut: Monkeyman.
First time Arnold meets Monkeyman.
Although most of the urban legends in Hey Arnold! are made up on the spot, Monkeyman can be seen as early as "Downtown as Fruits."
This is the second time - and possibly the final time - we see the guy who hates being called (from "Helga Blabs It All").
The title of this episode, "Buses, Bikes and Subways" is a parody of the movie Planes, Trains and Automobiles.
Willy Wonka & The Chocolate Factory
The scene which shows Chocolate Boy swimming in a vat of chocolate is similar to Augustus Gloop swimming in a chocolate river from the 1971 movie, Willy Wonka & The Chocolate Factory.
After Monkeyman changes his clothes and washes his hair. His purple suit and cane, is reminiscent of Gene Wilder, the actor who portrayed Willy Wonka in the original 1971 film.