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.
YMMV: All Grown Up!
Canon Susie: What flaws does Susie have, exactly? On top of that, consider this: Whenever it looks like a gig is going to be utterly ruined for Susie, it seems like the very laws of nature itself will go out of its way to ensure Susie is the one who comes out on top. See the episodes "R.V. Having Fun Yet? Part 2" and "It's Karma, Dude!"
However some other episodes do give her some realistic flaws such as the first episode where she is easily conned into giving a woman $1000 thinking it's for a record deal, another one has her struggling to juggle a music audition and an academic commitment and she's portrayed acting very petty and childish in the episode where Angelica stays with her. One episode also has her fed up with being called perfect by the other kids and goes bad for the next 20 minutes.
Also probably intentional, given that even though it's slightly less so here she's still intended to be the same Foil for Angelica that she was in Rugrats: Angelica thinks a lot of herself but has many flaws, so Susie is the all around better person who counteracts her - to her resentment. It's worth noting that almost all of Susie's best moments put her in comparison to Angelica in some way.
Contested Sequel: It is generally disliked by fans of its prequel due to its massive differences, and it never got the love its predecessor had. It barely lasted a few years, and with no legit movies.
Cult Classic: However, there are fans of the show who fondly remember it on its own merits, and to this day, there is still fanart/fanfiction of the show being created.
Creator's Pet: Harold appears more often in the later seasons of the show, sometimes even interacting with the younger kids in the absence of one, which hits a sore spot with fans of the original eight Rugrats.
Designated Monkey: Tommy becomes this in his preteen years, whenever his friends make him the scapegoat of their fury, whenever they're in a tight situation. This is done episodes like "Truth or Consequences", "Dude, Where's My Horse?", "All Broke Up", and "Brothers Grimm".
Die for Our Ship: Nicole, Rachel, Z and Nicholas for being the love interests of Chuckie, Tommy, Kimi and Lil, respectively. Strangely, a lot of them (save for Rachel) end up getting Put on a Bus, particularly noticeable with Z, who doesn't appear much save for a couple of non-speaking cameos at the start of Season 2.
Epileptic Trees: People were trying to figure out if Savannah Shane and Samantha Shane were one and the same girl ''(they do share a last name, after all,) despite looking and acting completely different. It doesn't help that Klasky-Csupo confirmed this rumour, right before Retconning it by having both characters appear in the same episode.
Fanon: Savannah and Samantha are relatives. The most common consensus is twins though them being half-siblings or cousins isn't unknown.
Morty is a parody of one. He's introduced to the group, tries too hard to be funny, and ends up widely disliked by everyone in record time.
Squick: The kids' reaction to Lou Pickle's Haggis.
Everyone's reaction to Phil's science experiment.
Tear Jerker: From the second episode where Lil moves out of her and Phil's room into one of her own. Just the moment where Phil walks into the room to find her stuff gone and sadly looks at pictures of them together as kids, ending with a shot of them in the mud from Rugrats.
Tommy's fate in "All Broke Up."
The Problem with Licensed Games: It may surprise a few that the series actually did get a couple of video games, one PC game based on the pilot, and one Game Boy Advance title which was a dress-up game starring the girls. Neither was remarkable, and both fell off the radar as quickly as they came.
Also, Samantha. Promoted as a possible love interest for Chuckie in the pilot, only to vanish from the show proper.
They Wasted a Perfectly Good Plot: "TP+KF" suggested it might finally have Tommy and Kimi become a couple, but is instead an episode where Chuckie believes Tommy is hitting on his sister and Tommy is trying to make it up to him.
The Unapologetic: Kimi Finster. She has said and done a lot of uncalled-for things throughout the series, from snapping at her own brother and friends, to anything else. However, any matter of conflict is magically resolve at the end of any given episode, with no one to callherout on any of it.
Uncanny Valley: The character designs may not seem like this at first, but when you notice the little things such as huge heads resting on tiny necks, it makes you wonder how they even turn their heads without falling over.