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.
So far even with little information of what is going to be in the game and where it's music will play, there are already quite a few catchy music tracks that have been revealed and made for the game examples are on here and here
Each character has their own level up tune and when characters are leveling up simultaneously the themes make the song "larger". Awesome music indeed.
And they'll be including some remixes from the original trilogy like this, a remix of "Battle Against a Dangerous Foe" from MOTHER 1 that incorporates the different parts of its remix "Sanctuary Guardian" from EarthBound
Funny Moments: On the site, hovering over the character sprites reveals their age, hometown, and favorite thing. Then there's Leo's:
Smoking Is Cool: Presumably Leo. Seen in the video link above, Leo is a smoker. And given the nature of any playable character in the Mother series being able to do some pretty badass things, from a monkey breaking a tank to a child destroying the existence of evil itself, Leo can be interpreted as this.