Nichijou

Season 1

Episode 27: OVA: Nichijou Episode 0

Mio Naganohara tries to comfort her friend Yuko Aioi when she gets a 1% score on a test. Meanwhile, robotic girl Nano Shinonome tries to give the young Professor, who has a cold, some medicine, which she refuses to eat, and tries to get advice from their talking cat, Sakamoto. Finally the Professor eats the medicine after Nano mixes it with pudding. Later, Yuko, Mio and their friend Mai Minakami go on a train ride, which is completely empty at this time of the day. Chronologically, this OVA most likely takes place some time after the 4th episode as Sakamoto is already a part of the family.