Maka's instant anger whenever Blair threw herself on Soul: was it out of actual annoyance and frustration, or was she jealous and didn't know how to express it through anything other than anger?
How much of Justin's actions in the latter half of the series were his own? It was made clear that he was often on his own a lot, and was often partnered with a Clown after his FaceHeel Turn. Clown's are beings of Madness and can drive people insane, and with Justin not having anyone to pull him back from the Madness or keep him anchored, he'd likely be more susceptible to Madness. So was Justin always just a follower of Asura, or did he get driven insane by the Clown and made a FaceMonster Turn rather than a FaceHeel Turn?
Anti-Climax Boss: Often, despite the build up of their threat, the villains tend to go down easily especially Medusa.
Awesome Ego: For those aren't annoyed by him, Black☆Star in all his hammy glory. Excalibur as well.
Death the Kid too. As is to be expected from a character with a very enthusiastic fan base, those who don't like him have to deal with the fan girls.
Spirit, he's either hilarious (and hot to his fangirls), or a creepy pervert who Maka is oh so justified in hating.
Maka. Either she's a flawed but overall admirable main character, or a presumptuous hypocrite. The debate especially gets heated when discussing her relationship with Spirit: some think she's justified in disliking him for the womanizing habits that drove her mother away, and some think she's not giving him a chance despite him trying and that her "All men are terrible!" mindset because of her father is immature.
Big-Lipped Alligator Moment: The scene of Kid in the Sphinx and finding the circular animal-thing, then kicking it away when he sees that it is asymmetrical, is never elaborated on
Broken Base: The fans appear to be divided on just how good this show is.
Chapter 113 has left very polarizing opinions. It is either seen as an extremely disappointing ending that shoehorns breasts in the first half and doesn't explain or resolve anything, or a really decent and fun ending that makes nice callbacks to the prologues of the series and ties up everything just fine. The fact that the heroes never have a rematch with Medusa who ultimately offs herself as part of making Crona the ultimate weapon didn't go over well either.
Ironically the ending of the anime likewise was a source of breaking. Some fans found the whole "Courage" can beat Asura ending rather cheesy and cliche while others thought it was a nice and simple metaphor for the series as a whole. Now that the manga has ended, most opinions on this have shifted to the latter since at least they managed to put down Asura in a more satisfying fight in the anime as opposed to neither side managing to overcome the other in the manga and Asura essentially rage quitting when he can't break the main heroes and sealing the moon.
Medusa Gorgon darkens the plot with her introduction. Using her own child, Crona, as a science experiment, Medusa drives him to madness without an ounce of guilt. Seeking to resurrect the monstrous Kishin Asura to bask in his destructive power, Medusa coerces two witches into helping her. Defeated by Stein, Medusa takes over the body of a little girl, taking advantage of the fact any harm the protagonists attempt upon her would harm the child she possesses. After Maka's kindness to Crona causes him to perform a HeelFace Turn, Medusa manipulates him into acting as her Mole within the Death Weapon Meister Academy (DWMA) and drive Stein further into insanity. When her older sister, Arachne, is revived, Medusa manipulates the DWMA into helping her defeat Arachnae, claiming she kidnapped Crona to bring Maka to her side. After getting the students to help her defeat Arachnae, Medusa kills her sister and takes her body and reveals to Maka she herself was the one who kidnapped Crona. Driving Crona further into insanity while she has him in her clutches, Medusa purposely gets him to murder her, completing her child's transformation into a psychotic beast to wreak havoc upon the world. Manipulative, cruel and destructive, Medusa wastes no time showing she devotes herself to nothing but spreading misery.
Too many examples to list. Suffice it to say that if you go three episodes without seeing something that qualifies, you aren't watching Soul Eater.
Black Star certainly qualifies. He constantly straddles the line between this and Too Dumb to Live. Slams squarely into the former, however, during the Rescue Kid arc. G.O.O.'s attempt to make him crazy just makes him more awesome and shakes the insanity off through a mix of being too proud and too stupid.
Stein is a frankenstein-y doctor those tendency for insanity makes him feared by both sides. The fact that he's also a Hot Scientist also helps.
Kishin Asura is a monster whose insanity can cause hallucinations by his presence.
The sheer menace of Justin's fully transformed self as a living guillotine makes it very clear as to why he didn't need a wielder to obtain Death Scythe status. Up until that point, he's simply been content with Blade Below the Shoulder, but when he fully transforms, he's got what are basically meat cleavers on the ends of Variable Length Chains, stocks to trap and sever the necks of anyone caught in them, and a seriously creepy Slasher Smile.
Marie gets this treatment a lot by Stein/Medusa and Stein/Spirit shippers, even though her relationship with Stein doesn't seem to be going anywhere beyond Ship Tease. By the end of the series, she's carrying Stein's child. Not that the shipping ever goes away, but there's at least one happy faction reveling in Canon.
Soul/Maka fans are scary, some fans have even reported being harassed at conventions for the "crime" of not shipping it.
Ear Worm: "Excalibuuur...Excalibuuur...from the United Kingdom...I'm looking for her...I'm going to Californiaaaa...".
Soul's older brother, Wes, is fairly popular, particularly with fanfiction writers. This is surprising given that every scene he appears in is either a flashback, or an illusion, that Soul is having. He never makes a proper appearance in series, and so what little we know of him comes from Soul's, most likely, skewed perception. But even so, he is more than often used in several fanworks.
Probably the only kishin that can be classified as this is Asura, if not only for that behind his mask, he is actually quite the Bishōnen. Too bad he rarely ever has his mask off. His introductory scene of him putting his skin back on didn't help either.
Ever since the ending of the manga, post-story fanfics have been popping up. Most of these address issues or concerns not touched upon in the ending proper such as how are Maka and Crona going to ever reunite given the latter's situation or the future of Stein and Marie's kid.
Everything about Maka's mother is another potential source of this.
It is also a very common plot point to have Hiro to meet and obtain a Weapon partner, usually an Original Character. Heck, Hiro in general receives more attention in fanfiction than the series itself.
For Death the Kid to talk to his father whilst in the field, he casts a spell by doing a couple of hand signs. The last sign◊ he does is American sign language for 'I love you'.
Having Justin be a very religious guillotine in charge of the DWMA's European branch might be a reference to a litany from the French revolution about "Saint Guillotine". Also in a case of foreshadowing or averting Artistic License Traditional Christianity, the upside-down cross is a very prevalent symbol on Justin's sleeves and his fully powered soul's guillotine which could account for either since while it is a Christian symbol used to show humility or as a tribute to St Peter it is often mistaken as a Satanic symbol.
Which makes for an odd comparison with Spirit. They are both loyal to the 'god' they serve. It just so happens that they're not serving the same being.
Germans Love David Hasselhoff: In Italy, apparently it was so popular among the scanlations-reading fans and such that the manga was translated and published because of it, and was quite popular for a long time. The fact that the anime was translated and aired uncensored (it's one of the few Italian dubs to include Precision F-Strike here and there) probably helped.
In the first opening, at one point Blair is seen jumping on a table in Maka and Soul's apartment with the whole gang over. Maka is disgusted/annoyed. Tsubaki doesn't seem to know what to think. Death the Kid and Black☆Star freak out, Soul gets a nosebleed. Patty and Liz, who were right near Blair, appear to be pleased with what they see.
Jacqueline and Kim, though it seems more from Jackie than Kim.
Crona and Maka, Maybe. The two share an extremely close bond, Maka being the sole reason Crona was first saved from madness, and Crona's devotion to Maka only being outclassed by their devotion to Medusa. When Crona snapped and almost became a Kishin, Maka desperately tried to save Crona before the rest of Spartoi found them and killed them, directly defying orders from the DWMA. Makadisobeyed orders. All for Crona. And it was thanks to Maka that Crona was able to suppress Asura and created the Black Blood Moon. It comes to a point where at times you have to stop and wonder if this is just friendship, or subtle Ship Tease.
Like You Would Really Do It: Chapter 112 ends with Spirit, Marie, Sid, etc trapped on the Moon thanks to Crona sealing away the Kishin, basically meaning they would have been killed off. Come Chapter 113 and it turns out Mabaa used her spatial magic to save them.
Moral Event Horizon: It's difficult to pinpoint exactly where Medusa crossed it, but forcing child!Crona to choose between killing a trio of bunnies or go without eating for five days is a good start.
Narm: The first half of the manga's final chapter. The side-effects of Crona's Mad Blood prison trickle down to earth. The population starts to act strangely based on that, manifesting as... an increased desire to fondle, urge, or otherwise think about breasts. Kid conjectures a new type of madness has been born and concludes it to be... the "Madness of Boobs." Now, this is supposed to represent Crona's desire for material affection, a completely legitimate feeling thanks to their backstory. This otherwise serious development is completely overshadowed by the ridiculousness of the Madness of Boobs.
Ships That Pass in the Night: Kid/Crona quickly became one of the most popular pairings in the fandom despite the fact that the two of them rarely, if ever, interact.
Somewhat Hilarious in Hindsight considering the end of the manga refers to the similarities in their upbringing and (intended) destinies, precisely the sort of thing shippers take as fanfic fodder. They are, in a technical sense, closer parallels than Crona and Maka.
They Wasted a Perfectly Good Character: Blair is absent for many of the major story arcs and her backstory is never given much details besides "a cat with magical powers." Tsubaki also gets only a couple of chapters to flesh out her character and then is basically resigned to a role as 'Black*Star's Weapon', reacting mainly to whatever is happening to him.
Maka's mom never shows up in person and is only mentioned in passing. She could've been a great way to shed some light on Maka's family life or introduce another badass character. Especially when you consider that early chapters hinted that she'd be an important character later on.
Poor Tezca Tlipoca... and he had to die more than once!
Mifune, Mosquito and Joe Buttaki.
For the villains Medusa as well.
Unintentionally Sympathetic: While no one is going to defend Spirit's failures as a husband, the story tends to pick on him rather excessively in spite of his honest attempts to be a good dad, while putting a happy face on Maka's not-exactly-there relationship with her Missing Mom. It doesn't help that Spirit's positive traits show that he really does his best for Maka, while Maka's mom never appears once or does anything to show she is even remotely worth Maka's praises for.
Values Dissonance: Zigzagged with Excalibur slurping his drinks. Slurping, while considered good manners in Japan, would sound obnoxious to someone from a Western country, including Excalibur's native England. However, we are talking about Excalibur here, someone who is painfully annoying to everyone. His obnoxious slurping would actually be in character to him. The English dub gets rid of the slurping, though.
Vindicated by History: The anime's ending was originally not regarded well, due to Maka defeating Asura with a single punch note Meant to symbolize her confidence in herself and her friends being considered very narmy. However, with the end of the manga many people found this ending a lot more satisfying than the manga's end, as in the manga Asura is not defeated and simply rage quits. It helps that the finale of the anime does setup this moment, whereas the manga was slightly criticized for not really setting up the finale really well.
What Do You Mean, It's Not Symbolic?: Among other things, Crona's name is a play on "Kuro na", translating as "dark one". And just for a moment, Lord Death and Asura's competing auras form a yin-yang symbol.
Crona might just be the woobiest woobie that ever woobed.
They may be the biggest one, but they're far from the only one. We have Maka with her massive insecurities, Soul with his inferiority complex (manga only), Tsubaki with her brutal sibling problem, Liz and Patti with their Dark and Troubled Past, Stein with his constant struggle to keep sane, Eruka with her forced servitude to Medusa under threat of death, heck, even Ragnarok could qualify (see Fridge Horror above).
Woolseyism: To reconcile Crona's Ambiguous Gender with English's lack of gender neutral personal pronouns, the English dub has characters default to male pronouns while it's clear that they are only guessing. For Medusa, who obviously knows Crona's gender, the ambiguity is preserved by having her refer to Crona as "it." Which is a perfect way of showing what she thinks of Crona.