If you download a pirated version, once one of your Sims doffs their clothes, the pixelation will keep spreading until it covers the whole screen, making the game unplayable. In interesting related news, it seems as though EA has included an amusing intentional anti-piracy glitch in the game. Realistic junk is, sadly, not a feature of The Sims 4 - still very Ken and Barbie down there.
You can download the nude mod right here, but don’t get too excited. This mod allows you to pursue your Sims dream of becoming a Porn Star or Adult Entertainment Producer in the Sims 4. I’m not sure why the makers of the mod used this picture to demonstrate it. Currently, WickedWhims doesn’t include general naked body overrides, like detailed skin or defined shapes, so these always have to be downloaded separately. There has been some kind of nude patch for every previous Sims game, and now the same can be said about The Sims 4! Sims bodies are divided into 4 parts head-top-bottom-feet and WickedWhims nudity system mostly uses the top and bottom half of the Sim body for undressing purposes. The Sims has always had an odd approach to nudity - nude models for all your Sims exist, they’re just censored by a pixelated filter when they disrobe, and modders are always quick to discover how to remove said filter.
The Sims 4 may have eliminated certain longstanding Sims “features” like toddlers and the ability to drown your Sims in the pool, but the proud tradition that is the Sims nude mod is still very much alive.