Nao looks over her 'Big Brother's Perverted Habits Diary,' looking over Shusuke's misfortune with seeking out various porn. (Source: Wikipedia)

The seven Blu-ray disc volumes of K-ON! have an extra short anime "Ura-ON!"

Mylene Hoffman, also known by the code name "009-1" is a beautiful cyborg spy. Instructed by her superior "Number Zero," she is assigned to eliminate a Jazz musician who is suspected to be a double agent. However, as she gets closer to the musician, she begins to slowly loses suspicions. Can she complete the mission before she falls in love? [Written by MAL Rewrite]

30-second sketches/omakes based around the events of the TV series with little twists.