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: Yuugen Jikkou Sisters Shushutorian
Crowning Music of Awesome: The show's opening theme "Omoidatta ga Kichijitsu", performed by Tokugaki Tomoko, Iwanaka Masako and Inabe Kumiko, who are collectively known as...guess what? Three Sisters! Full version with lyric here .
There's even an English version known as "Today is the Day". 
Wait till your heads go "Tilt", because here come the Three Sisters as in the show!