Most of these are done by copying from some comics that I read recently.
To me, copying is an important part of learning art, because it opens me up to new techniques and new method of expressions that I could apply in my own future artwork. In this practice, I try to study the poses and form of the characters. I could probably do another copy of the same comics to study the costumes, or the facial expression.
It is important to note that the purpose of copying is to study, not to copy blindly to achieve the exact likeness of other artist's artwork.