These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Acceptable Targets: The show preserves the grand Canadian tradition of making fun of Newfoundland. Which could actually be a bit of an in joke, considering that that's where the first season was actually filmed.
Alternate Character Interpretation: The animosity between Derek and Casey is just as easily explained by their being two Type-A personalities competing for dominance in the household.
Derek is either a bratty teenager who has no respect for rules or a growing sociopath, since he presents almost all the necessary traits: he doesn't care about other people's rights and feelings, hurting them without regretting at all, he constantly lies and manipulates those around him for his own personal gain, he constantly needs to hurt or insult someone to feel good (usually Casey or Edwin), he considers himself flawless and has the ego of a planet, he usually sees persons of the opposite sex as mere objects.
Derek/Casey, and how. To the point where 90 % of the show's fanfiction and posts were about the romance between the two of them. The actors themselves admitted they wanted to see Derek and Casey end up together.
The younger pair of siblings too, when they lock they lock themselves into the Closet together.
The Scrappy: Truman is seen by many as an unlikable character who constantly treats Casey horribly and seems to exist for nothing other than the writers to invoke the All Girls Want Bad Boys trope. Those who ship Casey with Derek or Noel generally despise Truman.
There's also one earlier on, when Casey's dad comes to visit.
It's for less than a minute or so, but in The Movie, when Marti vanishes and they find her canoe overturned in the water, Derek's obvious panic definitely qualifies.
When Casey says goodbye to Paul.
What Do You Mean, It's for Kids?: The early season had the characters explicitly talk about breasts, had an episode foucusing on feminism, Casey often accused Derek of being sexist, Derek and his step-cousin, Victoria, made out, which often made the viewers wonder if the show was directed at kids. Then there was the whole older audience of the show who only watched it for the amusement of seeing two step-siblings fighting their sexual attraction towards each other (even if there wasn't any, according to Word of God) and who was shocked when Derek and Casey didn't end up together at the end.