A recent question regarding identifying a Jack Stone minifigure included this surprising picture of the back of the minifig.
I was totally amazed by this because I had never seen a minifig with a leg pattern like that on the back. Was this unique to this figure for some reason? What could you do with this that couldn't happen with normal minifig legs?
As TheBrickBlogger has already pointed out, all of the figures from this theme are very different from a normal minifigure:
The backs of the legs on these figures are made to interface with Lego studs for seating purposes, which is probably fairly obvious. So, I am assuming that the holes with narrow gaps between them may be the focal point of the "unique shape" you mentioned. At first glance they appear to look very much like Key Hole Hangers, which suggests they may lock into/onto something.
But, after closer examination of a clearer picture, you can see that these slots provide clearance for the leg hinge assembly instead. This extra range of motion is well fitted for a theme based on "Action" scenarios. It probably provides some stress relief on the parts at the pinch point also:
The LEGO 4 Juniors figures (also called Jack Stone figures) are significantly different from regular LEGO minifigures. They are much larger, and are not intended to be taken apart like regular LEGO minifigures. They are closer to the LEGO DUPLO figures in this regard with non-removable head, torso, arms, legs, etc.
Having said that, if you remove the head with a hobby knife (yes, you have to cut through the plastic), the rest of the body can be taken apart into smaller components. Take a look at the picture below to see what a disassembled Jack Stone figure looks like. Source: http://thebrickblogger.com/2011/02/lego-4-juniors-minifig-customization/
