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.
Stella, too, because she is sometimes a stereotypical Dumb Blonde.
Big Lipped Alligator Moment: The part in season 3 episode 25 where Bloom is randomly attacked by a mud monster during the fight against Valtor.
Canon Sue: Bloom. Despite being the main character and getting more focus than the other girls in every season, Bloom doesn't turn into this until season three, when she gets much more screen time than in the previous seasons (Shafting both everyone else and every new plot element introduced), spends a lot of that time whining about her birth parents (that she never met) and home world (ditto) every five seconds. She becomes ridiculously powerful, to the point that Bloom in her normal outfit is more powerful than the other girls in Enchantix. This gets even worse in The Movie.
However, season four has fixed this.
A common complaint of the show is that Bloom gets too much attention and is a spotlight hog. It's to the point that many fan-fiction writers enjoy exploiting Bloom as a spiteful, selfish person while making the other characters woobies.
A lot of fans also feel that the plot is just a bit too good to Bloom. She gets her parents, homeland and later also her sister back. By comparison, look at where Musa and Aisha stand at the end of season 5. The former is still without her mother; the latter was again robbed of the chance of reuniting with Nabu. It doesn't seem fair, really...
The Sirenix theme as well, which is of a slightly surprising genre.
Designated Hero: Bloom. As explained below, she solely blamed Diaspro for ruining her relationship with Sky, despite that 1) Diaspro had no idea who she was, 2) Bloom randomly decided she was one of the Trix in disguise and attacked her and 3) Sky was essentially cheating on Diaspro with Bloom, meaning he deceived two people, not just one. Sky is also never held accountable for it.
Designated Villain: The witches of Cloudtower are considered evil and malicious by most of the fairies, but they're more on the level of the average "mean schoolgirl" and some of them even seem to be rather good-hearted.
Diaspro. Bloom blamed her solely for ruining her relationship with Sky, despite being Sky's fault for not telling Bloom about Diaspro (or about his real identity for that matter). The writers made her a JerkassRich Bitch so the viewers wouldn't like her.
Draco in Leather Pants: Diaspro is surprisingly popular among fans, despite the writers' best efforts to show how much of a Rich Bitch she is. However, the fact that she was made a Designated Villain in the love triangle between Bloom, Sky and her, plus many people's dislike of Bloom probably helped this.
Ear Worm: The "Believix" transformation music takes this to new levels.
In the game Quest for the Codex, you will have at least one of the tunes burned into your head for some time.
Diaspro and Chimera, count too, at least in their first appearance, when they really looked threatening.
Evil Is Sexy: The Trix, Valtor, Dark Bloom and the Fairy Hunters.
Family-Unfriendly Aesop: Many people felt that Bloom calling Mike and Vanessa by their first names instead of "Dad" and "Mom" gave the message that adoptive parents will never replace biological ones, regardless of how much they love you.
Both English show dubs are a lot better this by having Bloom call Oritel and Miriam her birth parents and she calls Mike and Vanessa Mom and Dad, but the movie is where this trope is TERRIBLE. She calls her biological parents her "real" ones, and at the ball at the finale, she calls Oritel, the father she's never known, "Dad", and when he surprises Bloom by inviting her adoptive parents to the party, she runs towards them while calling them by their first names. This happens within ten seconds of each other.
Oritel also later cuts in the reunion to steal a dance from Bloom, because it's a tradition for the father to dance with his daughter. He does this while Mike is standing right there, and nobody says anything. Oritel is still Bloom's father, but it would have been nice to see him offer Mike a chance to dance, too.
Here's another one involving Bloom (and she's the leader??!!), though it's a rather small one. After being betrayed by Sky, Bloom decides to leave Alfea and quit being a fairy, despite that she said at the beginning that it was her dream. Yeah, because your dreams are worth giving up over a guy who broke your heart. This is actually even worse in the comics, where it was explained Sky and Brandon switched places for Sky's protection and Bloom is just too darn hard-headed to listen to him. Even the vain Stella got over herself!
It gets worse when Bloom's friends attempt to talk her out of leaving. Their words fall on deaf ears and Bloom can't even tell them goodbye before she leaves. Apparently, Bloom doesn't think too highly of her friends.
Fanon Discontinuity: Some like to pretend "Royal Heartbreak" or anything following never happened.
First Installment Wins: The first season is the best-received and arguably the most memorable, and the others are criticized for creating good Plots and characters and then wasting them, having anti-climatic resolutions, the Power Ups and Frilly Upgrades causing the main characters to lose the beauty and their simplicity, etc.
Foe Yay: Darcy and Musa in season 1, because they both like Riven (albeit for different reasons).
Fridge Brilliance: Amore, the pixie of love being Stella's bonded pixie makes even more sense when you remember a comment Stella made in Season 1 about what she wants to accomplish as a fairy, such as being able to bring couples such as her divorced parents back together.
Fridge Horror: During the battle against Diana's plant monsters, Nabu at one point uses his magic to turn one of said plant monsters into stone. Why does Nabu know a spell that can turn things into stone?
The fact that S5 E2, about an oil spill, first aired in America during the same weekend that Hurricane Isaac occurred. What is the first event that comes to mind for this generation when it comes to oil spills, and where did this (and said hurricane) occur? Unintentional, certainly, but still a bit jarring...
Fridge Logic: If to access the Believix powers you need to get some one to believe in magic, then why doesn't Stella have hers before Season Four as she did this for Bloom, Mike and Vanessa?
Well, it's implied that Mike and Vanessa already believed in magic, but said nothing about it. As for Bloom, she already held a belief in magic and fairies from her childhood. It seems to gain Believix, you have to make someone believe in magic if they have no belief in it whatsoever.
"Funny Aneurysm" Moment - In the first season's finale, Lucy insults Alfea, and Mirta defends it. 4kids changes it to have Lucy making fun of Mirta, and Mirta saying she is transfering to Alfea. While this appears to be a plothole for the second season, this actually happens in the third season, although Mirta actually becomes a good fairy, instead of a "witch on campus".
Girl-Show Ghetto: When 4KidsEntertainment licensed the series for the United States, they insisted that boys would be able to like the show because the characters were sexy. Since the article also mentioned Ojamajo Doremi in passing, this led to some Unfortunate Implications...
Hate Dumb: On YouTube, there are quite a few "Sailor Moon vs Winx Club" videos. Not only does Sailor Moon win in every single one, but any viewer who thinks Winx Club should've won or even remotely likes it is immediately bashed.
Roxy. She was being hated on before season four even began and there are some people who hate her for no reason other than that she exists.
He's Just Hiding: Since Morgana promised to look after Nabu until he "wakes up", some are now starting to think that he might not be dead after all. Also, Lord Darkar and Valtor seem to get this treatment in fanfiction.
Hilarious in Hindsight: In season three Stella and Bloom try on dresses that look like a Shout Out to Jem. Then late in season four the girls form their own rock band. Coincidence?
Ho Yay: In Season 2: episode 13 Amore, the pixie of love, turned two of the thugs attacking Layla/Aisha and Musa gay.)
Internet Backdraft: When fans learned that Jakks Pacific wasn't going to make Musa and Tecna Harmonix dolls. Luckily, a few days later, it was revealed that they would be making them after all.
Les Yay: Moreso in the comics than the cartoon, as shown in this panel of Stella looking pretty happy when tickling Bloom and trying to prove she's not fat.
Flora is also bent on defending Pumpkin!Mirta and is ecstatic after turning her back. To be fair, that could also just be Flora's caring nature and considering how hard it was to change Mirta back, Flora kind of had every reason to be ecstatic.
Mis-blamed: Not everyone realizes there have been two English dubs of the show, so 4Kids sometimes gets blamed for faults in Cinélume's dub.
Now with Nick airing yet another English dub, Nick is being criticized for reverting some of 4Kids (what some people believe to be the original) edits and changes. Nick is/was also blamed for the one hour specials removing and changing some plot elements when it is actually the creator himself who directed the production of them.
Moral Event Horizon: Not only Ogron ultimately causes Nabu's death, he also steals the power that could revive him and wastes it, gloating to the poor Layla. No wonder she decides to join Nebula, still bent for revenge.
The Trix experience theirs when they turn the show's resident Woobie Mirta into a pumpkin while laughing maniacally.
Tritannus has been crossing it since he first appeared. Let's see: so far he tried to murder his own brother out of jealousy, then breaks out of jail by mutating the guards into horrible monsters, turned his family into horrible monsters, physically and physiologically tortured Daphne, attacked the Selkies and drained their powers, and attempts to turn his cousin Aisha into a horrible monster with a spell that gets Musa instead. So yeah, he’s not the nicest guy.
Narm: Nick's attempt at making "dragon sound effects" during Bloom's first Enchantix transformation is hilariously bad.
The ones for her "Charmix" transformation weren't too good either.
Valtor, for being a Villain Sue and then deteriorating rapidly.
In season 4, most fans really wanted Mitzi to just disappear already.
Screwed by the Network: The Nickelodeon hiatuses made some of the fans so angry that a letter campaign was started. A lot of people really just want the last three episodes of Season 5 to be released in America and for Winx to actually get a decent time slot.
Musa and Roxy also fit temporarily. Musa fit in the episode The Show Must Go On, where her father threatens to transfer her to another school if she performs in a concert just because he can't move on from Musa's mother's death (Musa has moved on). Roxy fit during the first few episodes of season four because she had no choice in whether to become a fairy or not. To sum it up, her choices were either become a fairy or be captured/killed.
Aisha is one too. In Season 2, her pixie friends were captured by Lord Darkar, and she at first had difficulty fitting into the Winx Club due to her lonely childhood. In Season 3, she was temporarily blinded by Valtor, and later was upset about her parents setting up an Arranged Marriage for her, until she actually met and got to know the guy, that is. In Season 4, Nabu died. And in Season 5, her cousin turned into a monster that is trying to take over the oceans, and she still hasn't gotten over Nabu's death, and a scene in episode 7 of Season 5 suggests that Aisha feels guilty about having been unable to save him.
And also in season 5, she has to deal with the fact that her cousin is the villain this time and not just some random bad guy like in the past. And she recently learned that her aunt, uncle, and two cousins were turned into horrible monsters by Tritannus.
Stella was one temporarily. She tries to hide it, but her parents' divorce had a shattering impact on her and it's implied she feels she's partly to blame. Then, in Season 3, she had hopes of her parents reconciling, only to have her hopes crushed by her father revealing he intended to marry a new woman, who almost became Stella's Wicked Stepmother. Also, her vanity comes from being teased about her appearance as a child, which could mean she's very sensitive to how others perceive her.
Daphne. Good lord, Daphne! Watching her endure torture up until her parents are threatened and then having her powers viciously ripped from her is too much!
They Changed It, Now It Sucks: Some of the responses to the Nickelodeon Winx Club specials created by RAI and the trailer for season five have been targeted as this.
As mentioned above, if a guy cheats on his fiancée with another girl, it's the fiancée's fault and she will become a Yandere if you don't back off.
Only men should learn about warfare and combat at a military school.
Although, this is kind of subverted with Aisha because she is a tomboy and as competent as the guys. However, since it's implied that her tomboyishness is rebellion from her childhood...
Musa and Riven's relationship. While no relationship is perfect, theirs has bordered on being emotional/psychological abuse. The fact that they both do have emotional issues does not help matters.
Villain Decay: The Trix and later Valtor. The Trix have recovered in Season 5, also thanks to a power-up courtesy of Tritannus, becoming a real menace again. Since the Winx are catching up with them, however, the three witches may take this route again.