What should I do with KK here?

[Greg Miller]

If you've run into the first person I've ever seen limp/call AA, then so be it. I'd tend to ignore that possibility.

The fact that he called your raise preflop somewhat reduces the odds of a made straight, but he's so loose preflop that I can't be sure. Does he call a lot of raises preflop? If not, it's probably not the made straight.

If I had to guess, I'd say he flopped a set or an OESFD and is trying to get the money in, in case his hand goes way down in value on the turn. If he's loose enough when calling raises preflop, he might even have top pair with an OESFD. Yikes.

I can't really see much of anything you're a favorite against except for a bluff. If he makes a lot of big bluffs, you might call. Otherwise, dump it.