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.
Common Knowledge: Ironically, while King Gator's out of place music number sticks in people's mind, they generally forget that King Gator does, in fact, return to defeat Carface andattempt to save Charlie (who dies from losing his life watch, nevertheless).
Belladonna's part of I Always Get Emotional At Christmas Time. It really has nothing to do with the plot and kind of comes out of nowhere, as the musical number is Killer's until she shows up and her part is mainly just to make it longer. Not that its a bad thing, it works very well as a Villain Song.
Complete Monster: Pre-Villain Decay Carface qualifies, as he's a murderous crime lord who will kill anyone who gets in his way with no remorse and was willing to kill a child. After Villain Decay, not so much. Red is even worse if you think about it. Since the first movie is technically still canon, Carface's deeds are. Red treats him like a small time thug instead of a crime lord, showing just how bad Red is compared to Carface. His ultimate plan was to suck all the dogs out of Heaven and then drag them to Hell, and the only reason he gives for it is "It Feels So Good To Be Bad". All his deeds aren't for personal gain like Carface's, they were for a sheer love of evil.
Belladonna most likely counts too.
Contested Sequel: While most fans of the first movie consider the second to be totally inferior because they say that it mostly lacks everything from the original, some say that it's a superior followup to the original because it's not depressing and it has a good story and catchy songs.
Nightmare Fuel: Charlie has a nightmare about his likely future in Hell and it's an incredibly frighting scene.
Tear Jerker: For many, particularly sensitive dog-lovers.
And if the story isn't enough, thinking about the aforementioned Reality Subtext will leave you in tears for sure, especially at the end of the movie.
When Anne-Marie overhears Charlie's rant to Itchy and mistakenly thinks Charlie doesn't really care about her, and of course the end when Charlie comes to say goodbye to Anne-Marie.
Timmy's fate in the Bad Future when Carface is shown, it's implied he's thrown out of his house and dies due to his leg...incidentally, this triggers Carface's Heel Face Turn.
Villain Decay: In the first movie Carface is an intelligent, treacherous psychopath, but in the sequels and tv series he's a cowardly, bumbling idiot.
Wasted Song: The credits song is nowhere to be heard on the soundtrack. And its a orchestrated jazz version of "You Can't Keep a Good Dog Down". It's quite catchy too. In fact, all of the instrumental score is arguably better than the songs, but are nowhere to be found.
The song that replaced it, "Love Survives", was a tribute to Barsi.