The ending of Turtle SoupAndRabbit Stew; Leonardo somehow ends up in Usagi's world and starts fighting a bunch of Ronin. Meanwhile, Usagi is fighting a bunch of Neko Ninja. The two, upon seeing each other, assume the other is part of their attackers and charge. At that moment, Leo goes back to his world and crashes into his brothers, while Usagi crashes into a tree.
Usagi:I HATE NINJA!
When Usagi first encountered and worked with Gen, Gen, in "good" humor (or whatever is considered good humor by his standards), cheated Usagi out of his hard-earned Ryo by leaving him with the bill at the inn they stayed at. During their second encounter and job together, Usagi got Gen back... by playing the exact same tactic against him. Doubles as an Awesome Moment for Usagi as well, showcasing how much of a cunning trickster he is on top of being a samurai.
In one short story, Jotaro wants to try and cut a plum seed off of Usagi's nose just like Katsuichi did back in the day. Usagi, rather wisely, insists they use a pumpkin as a fair substitute. Jotaro takes one swing of his wooden sword and...there's not much left of the pumpkin.