I caught a bunch of these the other day. I've been fishing 40+ years and I have never caught them before. I THINK I know what they are but they are not known to be in this water body. I was fishing a river eddy below a papermill dam on the Wisconsin River in Central Wisconsin.
 Here are some details:
the eyes are NOT red, 
the ear is like a bluegill,
the body shape of a rock bass,
the belly colorations of a pumpkinseed,
anal fin and tail is heavily edged in a dark red-orange,
pectoral fins are orange in color,
the mouth is larger than a bluegill, basslike,
beautiful neon blue streaks on the face and cheeks.
Any guesses?

Not sure, but it kind of looks like some sort of hybrid bluegill. Here is a link to one similar to yours. The only difference is that yours has blue lines on its cheeks, and the one in the link doesn't.

http://gallery.nanfa.org/v/members/farmertodd/centrarchidae/lepomis/hybrid/hybrid01.jpg.html

What do you think it is?

Salty Dan
Orange Texas

That is a Green Sunfish. Great little fighters. They are quite common in the lakes I fish here in Arizona. I catch  lots of them and use them for flathead catfish bait. I even have one in my aquarium my granddaughter caught 2 years ago when she was 10.

Green sunfish (Lepomis cyanellus) are members of the sunfish family along with bluegill (Lepomis macrochirus), redear sunfush (Lepomis microlophus), largemouth bass (Micropterus salmoides), black crappie (Pomoxis nigromaculatus), etc.

Yep...looks like a green sunfish to me too.