>>1963Anime-Mendo has a bit more of an edge than might be intended by Rumiko. he's meant to be a bit of a hot-head goof, whom in the moment will draw his sword on Ataru because he finds him so offensive and because he's a samurai traditionalist. Manga Mendo would probably not have shooting targets with Ataru simply because he would think thinking about him on off-hours is beneath him.
The animation team seems to have just loved Mendo though, giving him all these scenes and events. They kind of make him the "cool guy" that Rumiko is partially mocking to begin with. Guys just can't help themselves.