Cause of quarrel (When sleeplessness became the reason for a fight) (寝不足はケンカのもとでござるの巻) is episode 632 of the Ninja Hattori-kun 1981 anime.
After the roof in the attic leaks, Hattori, Shinzo and Kenichi modify the room to make more space. Yumeko, who is writing an article about friendship between ninjas and children - is in for the night! Kemumaki and Kagechiyo are there too - and they try to spoil Kenichi and Hattori's friendship!
Hattori and Shinzo are dozing in the attic, when the roof leaks. Hattori, who is awoken with a start, firmly asks Shinzo if he has wet his bed, to which he replies negatively. They then find the leak in the roof, and move into Kenichi's room, to which he and Mrs Mitsuba are most baffled about.
Next morning - or rather, that morning, Kenichi, disrupted by the shift, is still rather tired. Yumeko Kawai then tells him that she is writing about a relationship between a ninja and a young boy to the school magazine, for which she is staying the night at Kenichi's. Kenichi is ecstatic, but his joy is cut short when his two least favourite people come along with her: Kemumaki Kemuzou and his cat.
Later on, Yumeko takes photographs of Kenichi and Hattori flying on a cloth glider, playing computer games, and posing with cheeky grins on their faces. Evening comes and then they all go to bed - only for Kemumaki and Kagechiyo to come up with their usual antics.
That night, the new arrangements are shown; Yumeko on Kenichi's bed, Hattori and Shinzo on the ceiling, and Kenichi, Kagechiyo and Kemumaki on the floor. The plan that Kemumaki and his cat have hatched is that they cause diversions so that Kenichi and Kanzo's relationship will fall apart. First, they attach clothespins to Kenichi's nose, making him snore loudly. Hattori, disrupted, then scorns Kenichi, who is baffled and annoyed. Later on, Kemumaki and Kagechiyo throw a frog at Hattori, so that he shrieks in fright. Kenichi is extremely disrupted and snaps at his foster brother. A major brawl ensues - but suddenly, Kemumaki turns on the light. The boys then come to their senses, and watch in unison as Kemumaki tries to wake Yumeko up to tell her that the Iga and the Iga ally are fighting - only that it doesn't work.
Much later in the morning, Kenichi, Yumeko and Kemumaki are walking to school. Kenichi then waves to Hattori, who is flying his cloth glider and waves back. Kenichi and Yumeko then chastise a sleepy Kemumaki for being slow, for he stayed up he whole night.