Unfortunately, I couldn’t tell you how I got that pose. I know it was overlaying arm poses from these Parts posing boxes (here and here), as well as a game animation for the body pose and expression. The bat is from Around The Sims and is there with a shiftable OMSP.
I always play around with overlaying poses, but never record what I actually do so when I find a pose I like, I sometimes can’t remember how I got to it. I know that doesn’t help. >_>