"I love git-blame-someone-else!!" -Linus Torvalds says*
$ git clone https://github.com/jayphelps/git-blame-someone-else.git
$ cd git-blame-someone-else
$ sudo make install$ git blame-someone-else <author> <commit>
This changes not only who authored the commit but the listed commiter as well. It also is something I wrote as a joke, so please don't run this against your production repo and complain if this script deletes everything.
*Linus Torvalds didn't really approve of this. It's a joke to prove it works. See his fake commit here