Create Your Own Publishing Co. - What's Involved?

As I mentioned in another recent post, I’m helping a friend self-publish his novel. On the title page and copyright page of some books I know to be self-published, I’ve seen publishing companies listed, complete with a company logo. I’m assuming this helps mask that the book is self-published.

My question: how does one go about creating such a publishing company—one that has no intention of publishing other people’s books, but rather is simply created to be displayed on one’s own self-published books? Do you need to legally register the publishing company in the U.S., or can you simply make up any name and logo you want, slap it on the book, and pretend its real so long as the book itself is copyrighted, not to the publishing company, but rather in the author’s name? Thanks.