What is the copyright of meme pictures?

An image, including a meme, in the likeness of someone cannot be used without that person's permission. "Permission" of celebrity's virtually always comes with a fee. In that application one would also need the permission of the artist who created the image which would presumably come with paying for the image.

You don't get any copyright protection yourself when you commit copyright infringement. The copyright holder is the person who made the original image, or whoever they transferred copyright to. If someone is shooting video of professional sports, the copyright holder is indicated in the credits at the end of the broadcast, for example.

It's not "muddy." For things like memes, the main question is if it's worth the hassle of the copyright holder to go after people for such things. Sometimes they'll indeed issue takedowns.

I always understood it was the person who took the photograph, or produced the image, but professional photographers usually sell the rights to these photos to magazines etc., either permission to use once, several times or completely outright. I am not sure how you would ascertain copyright though. You will often see mention made, when asked, from the owners of the work, giving free use of certain images. But, it is always polite to usually ask permission first.