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.
The earlier strips had Dennis' Dad almost continuously spanking him with a slipper, usually to no effect; the only thing that could make an impression was Granny's legendary "Demon Whacker" slipper made from the hide of an African Elephant. This was phased out as corporal punishment of children fell out of favour.
In one old strip, Dennis' Dad spanks him for falling in luminous paint, even though it was an accident. In another, Dennis leaves home, and his parents repeatedly appeal for him to come home, but when he does, it turns out they wanted him back because he had accidentally taken the Darts Club funds with him — there's no indication that they were worried about their only child (then he gets spanked for running away).
Viewer Gender Confusion: The gender Foo Foo, Walter's pet poodle, seems inconsistent. It isn't just Gender Equals Breed expectations, Foo Foo also wears a pink ribbon, so many readers thought it was female, but the dog was usually referred to with male pronouns in the comics. However, in the animated TV series Foo Foo was referred to as female.
Unfortunate Implications: In the early cartoons and comics, Walter the Softy was picked on because he was effeminate, shy, delicate, physically weak, and essentially bucked gender roles. This gives the nasty impression, given Dennis's sympathetic portrayal, that we are supposed to applaud Dennis for punishing Walter for being different. Later works made Walter more despicable to compensate for this, sometimes making him snobbish and condescending, and others making him actively malevolent and simply using the facade of delicateness to avoid grown-ups' scrutiny.