Apparently, there's a bug in the code that won't allow the Groom to spawn (per http://wiki.terrariaonline.com/The_Groom ). Slime King isn't too hard to spawn, go to the edge of the map (but stay on grass), make a hut, put a water candle in your hand, and wait. I haven't found a really efficient way to farm piranhas. Maybe if you used something like my model, but extended the trenches out further? Or just use a single trench with running space above and below, and make it very long... as you run along it, piranhas will spawn and you can vilethorn them (or whatever you do) and collect prizes. Of course, I finally got my robot hat exploring an Overjungle, so meh.