Well if anyone was going to sue anyone it would be Disney, and so far Disney has never sued anyone who had one of thier characters tattooed on them (after all it isn't like they can remove it) However they have gone after tattoo studios who displayed their characters on their walls for people to pick as tattoos.
Interesting. I'm going to have to add this to the article I'm writing.
If it is a violation of copyright to have these images tattooed on you, no one seems to want to pursue it legally that I am aware of.
That's generally the way copyright works: something can technically be a violation of copyright, but no one really has an interest in doing anything about it, so it nominally stays in the realm of the "ok." All the same, if I* were a tatoo artist, I'd shy away from tatooing a picture of Mickey in sexual acts with Donald. It would be like tatooing "SUE ME" on the guy's forehead forehead.
after all it isn't like they can remove it
That would be an interesting court order: "The court hereby enjoins the defendant from wearing short sleaves. . ."
* i.e., this is not an official legal opinion and no one reading it should rely upon it. Official disclaimer over.