Hattori bothers Mr Koike or Hattori recovers his Honour (名誉かいふくの巻) is Episode 10 of the 1981 Ninja Hattori-kun anime.
When Mr Koike comes to call at Kenichi's house, Hattori disobeys Kenichi's commands to stay upstairs and not poke his nose.
One afternoon, Kenichi tells Hattori, Shinzo and Shishimaru that his teacher, Mr Koike, is coming to visit, and orders them to stay upstairs whatever happens. He goes downstairs just as Mr Koike arrives. As the teacher is about to open the door, a ghost opens it - and Mr Koike is afraid of ghosts. The ghost closes the door, then sorts Mr Koike's shoes out. Neither Mrs Mitsuba nor Mr Koike know who it is, but Kenichi does...
Upstairs, Kenichi shouts at Hattori for snooping and storms out to serve Mr Koike his tea. He and Mrs Mitsuba give Mr Koike his cup and saucer and leave him to it - but when Shinzo's refection appears in the cup, Mr Koike gets such a shock that he drops his cup and spills his tea across the carpet. Kenichi is furious with Shinzo and orders the naughty little ninja to remain upstairs.
Once Mr Koike has had another cup of tea, Mrs Mitsuba asks Kenichi to show Mr Koike his room. Panicking, Kenichi lies to Mr Koike that his room is dirty, but Mr Koike joins him regardless - the truth is that Kenichi's room is squeaky-clean, except, maybe, for the mischievous ninjas. Mr Koike jumps in fright upon seeing Shishimaru hanging on the wall, but Kenichi distracts him by giving him his Rubix cube. Mr Koike solves the puzzle very quickly though, and trouble strikes when Shishimaru loses his balance and falls on top of Mr Koike, knocking him out cold. As he slips out, Mr Koike comes round.
Later on, Kenichi and Mrs Mitsuba say goodbye to Mr Koike. As he leaves, Hattori repeats his actions and jumps into Mr Koike's shadow. Halfway through, he jumps out, and a terrified Mr Koike dashes home.