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.
"Stray Bullet", from comic book story "Squirrely Burly" (issue #1).
"All Chalked Up," from Scholastic Book, same title.
"PowerProf.," from Scholastic Book "Powerpuff Professor."
"Substitute Creature," from Little Golden Book, same title.
"Neighbor Hood," from comic book story "Remote Controlled" (issue #7). The episode was originally penned for season 1 but fearing a lawsuit from the producers of Mister Rogers' Neighborhood, the outline was given to DC Comics for the comic story.
"Lying Around The House," indirectly from comic book story "Big Fish Story" (issue #21).
"Simian Says," indirectly from comic book story "See You Later, Narrator" (issue #46).
"Deja View" (comic issue #50) was intended as a season 5 episode but was shelved due to being overbudget (half of the ep was to be in CGI) and having a tight deadline. Like "Neighbor Hood"/"Remote Controlled," the story outline was given to DC and made into a comic.
Alternative Character Interpretation: Him's Camp Gay tendencies are an act to trick his enemies into letting their guard down. He occasionally slips out of the act when angered or excited, before quickly realizing his mistake and going back to acting.
Professor Utonium reveals in "Keen On Keane" that he does, in fact, remember how he was once brainwashed by an evil cat, yet he acted like it was All Just a Dream at the end of "Cat Man Do." Did his memories eventually return (not uncommon in post-Brainwashed and Crazy cases)? Did he make the girls fill him on the weeks (days, at the least) he couldn't remember and explain how he ended up outside that building in the middle of the night? Or was he merely pretending he couldn't remember to try to make it easier on the girls?
In "Insect Inside" Blossom produces a giant jar to contain a mass of cockroaches. Lampshaded by the narrator who talks about Blossom's knowledge of where to get giant jars, and in a later episode where she pulls out a giant match, which she claims to have gotten from the same place.
During "HIM Diddle Riddle," the girls are tasked with taking down a giant monster without using their powers. Buttercup runs off and comes back in a helicopter with a gatling gun. Where did that come from, how did she get it, and how does she know how to pilot it?
Badass Decay: The first episode Him was introduced, he was presented as a hellish almighty powerful being so fearsome we can't even say his name, and was pretty solid Nightmare Fuel. By the last time we see him in the show he turned into just as much of a feeble joke as any other villain.
Though somewhat justified as Him draws power from evil, the more good around him the weaker he is.
And we've seen what would happen if he won as well, and it's notpretty. He may not be as deadly when last seen, but he's no doubt still dangerous to be taken lightly.
Big Lipped Alligator Moment: At the start of the episode "Catastrophe", the girls are shown at a ceremony where they are rewarded with a bronze statue and "Powerpuff Day". The ceremony is soon interrupted by a monster searching for his cat, who the girls leave to deal with. The ceremony is never mentioned again throughout the episode. .
And now that the special itself has aired, opinions are divided on if the special was a fun and fast paced trip down memory lane that should lead to a revival series, or if it was a rushed mess that needs to just stay a one off. There is something of an agreement that the last few minutes of the special felt rushed and that it would have benefited from being longer, but whether or not if a person thought the rest of the special was good or not is, naturally, a matter of opinion.
Complete Monster: Season 4's two-parter "Knock if Off" has one-shot villain Professor DickHardly. Introduced as the sleazy college roommate of Professor Utonium, Dick quickly sees the potential of the Powerpuff Girls as a way to get rich quick. Getting the girls to supply him with Chemical X, Dick makes his own knock-offs of the girls and starts a business selling these copies as superheroes. Due to Dick's greed, however, these knock-offs have been created with minimum materials and Chemical X, meaning that, even though they are aware, they are mentally stunted and physically deformed. When the effort of superheroing causes the knock-offs to literally fall apart, Dick's happy because it means he gets to sell even more copies. At one point Dick notices one of his knock-offs is a perfect Buttercup copy, his response is to order the girl melted down for her "excessive" Chemical X. The episode's climax has Dick capturing the real Powerpuff Girls and killing them slowly by draining them of their Chemical X. When Utonium offers to be a slave, making Chemical X for Dick for the rest of his life, if Dick will let the girls live, Dick only laughs and says he'll kill the girls and keep Utonium as a slave. Greed incarnate, Dick Hardly was notable for being the only villain on the show to be played completely seriously, with no humorous quirks to detract from his viciousness.
Designated Hero: The Squirrel from "Fuzzy Logic" is treated as being a hero, even though Fuzzy's rampage in Townsville was partially his fault, and apparently never felt it was important to bring that up.
Designated Villain/Unintentionally Sympathetic : Blossom at the end of "A Very Special Blossom", sure, she stole something, but she felt bad about it, and she had only stolen the golf clubs so that she could give Professor Utonium a present for Father's Day.
Similarly, the ending of "Slave the Day" where they viciously beat Big Billy for helping the rest of the Gangreen Gang capture them, even after he remorsefuly turned against them and saved their lives.
Ensemble Darkhorse: The Rowdyruff Boys were intended to be one shot villains, but they garnered such huge fan support with tons of fan art to even a website built around them (which is unfortunately now disabled, the link is to a archive of the site) that the writers eventually caved and brought them back, redesigned and having more depth then just being evil counterparts to the girls.
Bunny, the fourth Powerpuff Girl that Blossom, Bubbles, and Buttercup made, has some love from the fan-base, probably due to her episode being an absoluteTear Jerker. She's even mentioned in Bleedman's Powerpuff Girls Doujinshi.
Fan-Preferred Couple: A fair portion of the fanbase were in favor of Professor Utonium and Ms. Keane hooking up. Alas, it was not to be. (So far.)
Family-Unfriendly Aesop: In a society where children are told to cooperate, we have the episode "Monstra-City". An episode that shows the complications of immigration/integration. In the end the only thing they learned was that not everyone is able to live together.
On a related note, Bubbles' love of unicorns gets amusing when you note who her voice actress started voicing on Lauren Faust's other show. This pic sums it right up.
In the episode "Collect Her," the villain is Lenny Baxter, a guy who buys all the PPG merchandise and then kidnaps the girls when he's completed his collection. He's a nerd who lives alone, surrounded by toys intended for children. Does This Remind You of Anything?
Remember how "Meet the Beat-Alls" was an episode full of references to The Beatles and even contained animated cameos of younger versions of Beatles members? For the 2014 special they actually managed to get Ringo Starr himself to be a guest voice, and prior to the special's airing made a song and music video called Wish I Was A Powerpuff Girl.
"All Chalked Up":
The scene where Buttercup destroys Bubbles' chalk in "All Chalked Up" becomes extremely ironic when you remember that Buttercup's voice actress E.G. Daily is also the voice of Rudy Tabootie.
Ho Yay: In the episode called "The City of Clipsville," Professor Utonium is about to marry Ms. Bellum. But then when he takes off her veil to see her face, it turns out to be Mojo Jojo who reveals that he has always loved the professor. This is also a serious example of Getting Crap Past the Radar.
Jerkass Woobie: Buttercup full-stop, if you think about it long enough. First of all, the professor had no good reason officially to name her Buttercup other than that it starts with "B". Second, she has no unique power (and tongue-rolling doesn't count). Finally, nobody really pays her any attention, and when they do, it's usually when she's in trouble. Even some fans never seemed to care much, instead opting to exploit her misery and attitude for kicks and giggles.
Jerk Sue: Elmer when he was turned into a monster. Yes, he was being bullied, but he attacked people that didn't do anything to him, and the only person he calls him out for it is Buttercup, who is treated as being in the wrong for not apologizing to him even the things he's doing are much worse than what she had.
Love to Hate: Him. He manages to be one of the most popular villains in the series to be incredibly frightening and efficient, especially in the earlier seasons.
Mojo Jojo as well. And Princess. And the Gangrene Gang. And Sedusa. Not so much the less evil Fuzzy Lumpkins or the completely hapless Amoeba boys.
Dick Hardly. His one appearance means it's the primary reason for his popularity.
Magnificent Bastard: Him, mainly in his earlier appearances. Sometimes Mojo Jojo, particularly in the movie.
From "Cover Up," a floored Buttercup's pathetic "Nooo" when a rather diminutive monster marches toward her. She just let herself get beaten up because she hadn't rubbed her good-luck blanket, but when taken out of context, this clip has some rather Unfortunate Implications. Needless to say, without context, Poopers had a field day remixing this clip.
Misaimed Fandom: In the Clip Show spoofing episode, one of the "flashbacks" was of the Powerpuff Girls being bimboish teenagers who have given up crime fighting to hang out at the mall and flirt with the also teenaged Rowdyruff Boys. The whole sequence is rumored to have been a parody of extremely bad PPG fanfiction. A great deal of fans completelymissed the point however, and the sequence ironically ended up inspiring even more fanfiction with similar plots.
Dick Hardly murdering a perfect Buttercup clone for her Chemical X. And later on, tries to kill the real Girls for more Chemical X.
Mojo crossed it in the movie by enslaving Townsville with super monkeys, destroying half the town, and betraying the girls trust in the process. Since it was his first evil world domination plan, he apparently couldn't cross the line any further in the TV series. See Villain Decay.
In-universe example, Played for Laughs: in Twas the Fight Before Christmas, Princess switches the nice and naughty lists to make it look like she's the only nice kid in the world. As soon as Santa finds out about this and actually sees how naughty Princess is due to her rubbing her demands on wanting to be a Powerpuff Girl in his face, he has no choice but to induct her onto the Permanent Naughty Plaque.
One Episode Wonder: Dick Hardly. Indeed, while he came late in the series' lifespan, his episode is considered the best written within the Seasonal Rot and many fans even put him above Him as their favorite villain.
Paranoia Fuel: The episode "Supper Villain" hammers in that your average, everyday neighbor with an average, everyday family could actually be a sociopathic supervillian wannabe without anyone knowing it.
Periphery Demographic: At the peak of popularity, most of the show's fans were boys... not that every guy would admit to watching it in public.
Nowadays it seems fine to admit you watched this show. It was intended for both boys and girls though.
Poor Man's Substitute: Craig McCracken originally wanted Jack Black to voice the Gnome in "See Me, Feel Me, Gnomey" but by the time they got to production he was too busy and expensive, so they instead got Jess Harnell doing a Jack Black-like voice.
Special Effect Failure: There are some points in the series where you can clearly tell that characters have been chroma-keyed into the scene.
Of the four seasons that were under Craig McCracken's supervision, season two is often regarded as the weakest. Although it does have some fan favorite episodes such as "Beat Your Greens", "The Powerpuff Girls' Best Rainy Day Adventure Ever", and "Speed Demon", several episodes of it often crossed the line into Sadist Show territory and often relied on using an Idiot Plot more than anything else.
Seasons five and six were after Chris Savino took over as showrunner mark a noticeable decline in quality, making the jokes much more cruder than in previous episodes and putting the characters through very noticeable Flanderization.
Strawman Has a Point: Buttercup's attitude's towards Elmer after he became a monster. She's treated as being in the wrong for refusing to apologize to him after bullying him, but as she points at, Elmer was attacking people that didn't even do anything to him, including his teacher that actually stood up for him.
They Wasted a Perfectly Good Character: Similar to the below mentioned "Beat Alls" example, Cartoon Network actually did manage to get former Beatle Ringo Starr to guest star in the 2014 computer animated special as a math themed celebrity named Fibonacci Sequin, but he doesn't get many speaking lines (though he does drop a hilarious Beatles reference at one point) and never sings (odd when one remembers that dancing played a part in the special's plot). At the very least, though, CN and Ringo did make a song and music video called "Wish I Was a Powerpuff Girl" that aired during commercial breaks leading up to the special.
Villain Decay: If we look at things chronologically from the movie to the TV show, this happened to Mojo Jojo. He actually succeeded in taking over and destroying much of Townsville in the movie but is always failing in the show. He did, however, have the girls' help in the movie. They weren't so easily tricked afterwards.
More or less happened to a few other villains as well in The Movie. Before the Powerpuff Girls were around, the Gangreen Gang were a very frightening street gang. In the show, they often needed the help of someone else to even be considered a threat.
Him during "Meet the Beat-Alls" goes from usually being a bigger than threat than any of the other villains in the episode, at times more so than all of them combined, to being nothing more than just a another member on a team and is easily overpowered by the girls even with help from Princess and Fuzzy, even though the latter has been able to fight all three of them on his own.
Villain Sue: Done on purpose with the Alien Force from "Forced Kin"... until the end.
What an Idiot: Princess insulting Santa Claus in front of him in the Christmas Special.
All three Girls fall under this in "Sweet 'N Sour" where the Fluffy Bunch is robbing Townsville blind due to their blatant cuteness. It's hard not to wanna hug all three girls when the whole town turns on them and denounces them as animal haters.
What with the Adult Fear he goes through several times, it's hard not to feel bad for Professor Utonium, especially if one is a parent themselves.