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: Onegai My Melody
Jerkass Woobie: Kuromi is meany all because My Melody really made her life miserable.
Mana, considering the fact that the incident with all of the cute stuff made her a Jerkass to My Melody.
Wangst: Keiichi Hiiragi's reaction to coming second in a violin competition: he smashes his priceless Stradivarius, and goes into catatonic BSOD lasting for days.
Although it wasn't really so much coming in second as it was that the guy that beat him was able to play the Song of the Dark Power.
When Uta discovers Keiichi is the one who fuels Kuromi's magic, she goes into Heroic BSOD for at least one day.
What Do You Mean, It's for Kids?: One episode features a girl who uses magic to make her chest bigger by "stealing" size from other girls. Blood can be seen in one episode after Keiichi comes in second place in a violin competition.