I'm hoping this is an okay place to put this, since you can't really call a canon pairing "crack."
I know our focus is NS, but I was a little sad to have not yet found much discussion of those outside the main two couples.
On the one forum I occasionally visit, I was surprised how weirded out people were about this pairing. I thought I might share my thoughts, in case anyone here was equally weirded out by these two.
A story-based explanation of Choji and Karui:
Naruto wanted the ninja nations to come together in peace. What better way to show he succeed than to have people from other nations marry Konoha people? There's always been that 2 guys/1girl issue with teams, so picking a girl from another nation makes sense. Karui is the only Rookie-aged kunoichi we'd met from Cloud, so it makes sense she'd end up married to someone in Konoha for the sake of the story.
Also, Naruto, Sasuke, and Shikamaru were already taken, and apparently Kishimoto was more interested in making fun of Kiba and Shino and Lee (sort of) to marry her off to one of them. That leaves Choji, proud heir of his clan, a man who would feel a responsibility to have kids.
A personal explanation:
Karui grew up with the strongest, most admirable men of her nation being hefty, so she wouldn't find Choji's size an issue. Also, most men are probably neither strong enough nor easygoing enough to have her for a wife.
Choji is both strong and easy going. He also dreamed of finding a wife and worried no one would like him because of his weight. If Karui said she was interested in him, that would probably have been enough for him to fall for her. Never underestimate how attractive being desired is to someone who is usually rejected by the opposite gender.
Don't you think he'd be an awesome dad? I liked their kid best--she had sass!