Its still theft. Popular meme or not. Why? Because they surely did not receive permission from the owner of the art to do so. Had the person redrawn it them selves then that's a different story. They are using someone else's work to gain popularity.

Yes, there are tons of bases on the internet that allow you to fill in the details of a character, but those too are for the most part made without permission of the artist.

Something being accepted by many doesn't make it right. Specially when you go about telling people that you did it all with your own skills.