Is it possible to use Puppet Pin on a 3D space? I am animating one of those "man / woman" pictograms and I need its legs to be distorted in 3D (for simulating a running motion).
Nope. You'll have to use Freeform (comes with AE CS5 and 5.5) or other tools for that. Depending on what you wanna do, you might even do it oldschool with plain 3D layers parented to one anotehr...
I second Mylenium's recommendation for trying Freeform. Here's some information about it: