I'm working on taking one apart actually.... I just haven't had time to sit down and get more than the part on the back out.... basically if you cut around the seam for the hard plastic in the back, you can get that loose and pull it out, I haven't taken the head off yet.
eta: if you heat the pony up, you can sorta force the soft plastic and the hard plastic to separate from each other, making it easy enough to remove the bucket... you just have to work at it slowly by boiling it, and using an xacto knife or a tiny screw driver very carefully