Is Olga genuinely trying to be a good sister to Helga, or is she just a passive-aggressive version of Jamie O? It doesn't help that at least one Olga episode ("Student Teacher": when she tells the story of Helga wetting in the bed and gives her detention after she gets angry at other kids teasing her) almost seems to be written with this interpretation in mind.
Then there's this comment from the episode "Big Sis"...
Olga: I just love having a little sis, Lila. Especially one as perfect as you.
Exactly how much of Pookie's behavior is senior senility and how much is Obfuscating Insanity? And how much of it is influenced by what happened to her son and daughter-in-law?
Lila creates a lot of different interpretations. There are elements to support her being either a manipulative Bitch in Sheep's Clothing hiding behind a mask of sweetness, or a Stepford Smiler trying to be as sweet and smart as can be while having a difficult life. Or maybe it's both, and the latter led to the former. Her behavior in "Timberly Loves Arnold" suggests the former, while her audition scene in the following "Eugene Eugene" suggests the latter. Word of God is that she has a repressed darker side (which was never shown in the series); however, this just adds fuel to the fire. Then there's the Unrequited Love Switcheroo between her and Arnold, and Lila being the Master of the Mixed Message. Some suggest that she intentionally led Arnold on and gave him false hope (see: the end of "Love and Cheese"), while others suggest that she genuinely got over him while still caring for him deeply, and turned Arnold's advances down to stay out of the way for Helga's sake.
Her attraction to Arnie. Is it a case of Birds of a Feather, since he comes from the country like herself and can relate to him? Or does she actually recognize that Arnie has autism, while nobody else does, and see some Hidden Depths? She does treat him nicer than she does Arnold, as there are no subtle manipulations in play.
How innocent are Helga's intentions with Arnold? Does she really love him? Or is her "love" really just an unhealthy stalker-like obsession? She always maintains a cruel, bullying persona whenever she confronts him because she's terrified of him rejecting her. While it's understandable, it's not really excusable and there's very little for Arnold to love if all he's ever known is a petty, mean bully. She does selflessly do things for Arnold every now and then, but more often than not she only helps Arnold out if it means he might return her affections, which often comes across as the Entitled to Have You mentality.
Big Bob Pataki. Abusive jerkass or simply an ignorant boor who just doesn't understand how much trouble he's caused for his family? The latter characterization became steadily more common from Season 2 and onward. In the first season, he was portrayed as pretty much devoid of redeeming qualities, but even in the later seasons he had more than a few Kick the Dog moments.
A disturbingly common theory amongst fans is that the ending of "Pigeon Man" actually has the titular character commit suicide, usually arguing that the scene of him being carried away by his loyal flock is actually a traumatized Arnold reinventing things in his head to cope with seeing his new friend jump off of the roof. This was thoroughly, thoroughly jossed by show creator Craig Bartlett, and officially jossed in Hey Arnold! The Jungle Movie, which showed the Pigeon Man alive and well, happily living with his flock...in Paris.
Is Eugene actually jinxed? Every one of the misfortunes that befalls him are all in Arnold's presence, and sometimes even caused by Arnold. Is Arnold inadvertently causing bad things to happen to Eugene? The episode "Eugene's Birthday" even examined this.
Did Arnold refuse to rat in "Full Moon" because it "wouldn't be right", or did he keep his mouth shut because he wanted Harold, Sid, and Stinky to come clean by themselves? Then again, considering Wartz was being a petty jerk to Arnold, even getting Arnold's name wrong several times, and doesn't even offer him compensation for the time he's had to spend, maybe he refused to snitch just to spite Wartz.
Does Arnold really want his peers to be better people? Or does he just try to help them because he's annoyed with them and wants them to change? Some people would even go so far as to say his advice is just bluffing and he doesn't actually practice what he preaches.
Helga being head-over-heels for Arnold is a core part of the show, but does she really have a Single-Target Sexuality? "What's Opera, Arnold" implies that she sees Curly as fit to play a dashing rival for her affection, and wants to give Stinky a real chance with her after they'd pretended to date.
Some viewers have examined certain moments between Rhonda and Nadine and found that they might actually be Nadine passive-aggressively trying to get back at Rhonda for steamrolling over her and her opinions. For example, in "Rhonda's Glasses", Helga mocks Rhonda for getting gum on her clothes without noticing, at which point Rhonda angrily demands to know why Nadine didn't tell her about it; Nadine is never shown actually answering this question. Did Nadine really not see the gum? Or did she keep quiet about it because she wanted Rhonda to be taken down a peg?
In "Eugene's Pet", Eugne acts like he got a hippopotamus as a pet after the accidental death of his goldfish. Was he just trying to cope by creating an imaginary friend? Or did he temporarily snap and genuinely believe he had a pet hippo?
"24 Hours to Live" sees Harold respond to Helga calling him "Blimpo" by saying he has a glandular problem. Was he just being defensive, or does he genuinely believe it? If the latter, is it actually true?
Gerald keeps commenting on how good Sheck looks in a suit. Is this platonic admiration, or is he attracted to the man despite himself?
What does Arnold actually believe pertaining to Helga's Love Confession? Does he actually think she just gave into a moment of high tension that made her feel like that's what she meant? Was a suspicion Arnold had about Helga having feelings for him confirmed or did he really not realize? Also, by asking Helga if she actually just got exasperated and blurted it out without thinking about it, is Arnold giving her an out and allowing her to take it back until she actually is ready? The Jungle Movie does basically seem to confirm that in both that case—and when Helga tries to confess on the boat—that the former was both Arnold and Helga not being ready to have that discussion while the latter was Arnold himself not being ready for it.
Lasombra refusing to give Rhonda the Wi-Fi password. Was it a case of Evil Is Petty or Pragmatic Villainy considering that if she had internet access, she could easily message someone to rescue the kids from his prison? Doubles as Fridge Brilliance.
Curly offering to join up with Lasombra and his goons: Curly being his usual psychotic self or secretly trying to instill himself as a mole to give his classmates a better chance for an eventual escape?
