David always falls for the Batman patented Sucker-Punch-the-Guy-Behind-You move.
Back when I first started getting the idea for this group, I've always had Shiina and David partnered up, even though he could be just another member without being particularly bound to the others. Since they're exact opposites of each other, I figured I could get a lot of comedy out of the classic odd couple act. And since Shiina's the physically one capable of the group, that means plenty of fortuitous violence at David's expense.
I also like that she seems to be the only one who can harm a mostly intangible ghost. Does she have some strange power? Does David secretly like the abuse and let her beat him up? Who knows?!
I also did a size comparison so I know how they look amongst one another. I did a few minor tweaks to Samantha's and Shiina's heights, but for the most part, I like them they way they are now. As my three readers could probably tell with the comics of John and I, I like height discrepancies between main characters. I'm not really sure why, honestly. Maybe it's just from watching cartoons of the Disney trio while growing up.