My favorite short loop hike in the Smokies is the Gabe's Mountain/Maddron bald/Snake den ridge loop. It's a 2-nighter with tons of beautiful creeks, some old-growth forest, nice waterfalls, and some scenic mountaintop views. If you wanted to push that to a 4-nighter, you could integrate a short AT section to take you over the TN/NC border to the Big Creek area on the NC side. From what I've heard, there is some decent fly fishing to be found along Big Creek. Spend one night at campsite 36 or 37 then take another day to the top of Mt. Sterling and camp at 38 (see map below). Get some amazing panorama pics from the fire tower on Sterling, and backtrack down Shallow Fork/Low gap back to the cosby access area. It would be a long final day, but definitely doable.

http://www.nps.gov/grsm/planyourvisit/upload/GSMNP%20Backcountry%20Map.pdf

Pretty decent trail map, and combine it with terrain/topos from google maps, and you can get a decent idea of what you'd be in for. Most of my hiking in the smokies is concentrated in that general area, so hence my recommendations.

The good thing about GSMNP is that there's tons of information on various hikes floating around online. That also comes at the expense of some of the trails being more populated, and less conducive to getting away from people

edit: forgot to mention, if you play baseball for Wisconsin...BOOOOO!