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.
Most Annoying Sound: His iconic yelp, which quickly becomes insufferable whenever he's in distress (which happens a lot). Thankfully toned down in more recent cartoons, where he more stereotypical dog vocalisations.
Nightmare Fuel: Plutotopia, why is it so? Well, Pluto in a dream is tormented by a talking cat that addresses him with sarcasm and a suicidal sadomasochist to boot. It shows why cats and dogs should hate each other because this solution is disturbing.
Pluto's headshot from the original opening titles of the 1940s RKO shorts. It's overly symmetrical appearance can be quite unsettling to first time viewers. Fortunately, a more standard, cheerful title card replaced it later on.
"Pueblo Pluto" has the scene where Pluto is trapped in a cactus patch, and starts panicking so much he starts imagining all the cacti coming to life and lunging after him. You ever think a cactus couldn't be freaky-looking? Think again◊.