One of the current opinions of Netporn experts, is that many unusual images are produced only to fill gaps, to explore every possible fetish and practice. In many cases this is certainly true (as in the eye cumshot, for example), but there are many pictures that seem to confute this idea. Like this one:

It’s part of a long series that features a slug while exploring a man’s shaved genitals. The close contact, slow pace and inherent humidity of this operation suggest much more than just a quest for the unusual.