I have a Magic Chef refridgerator that doesn't shut off. It has ran for the last 10 days. The freezer and refriderator are cooling just fine and seem to be okay. The door seals are good also. What would cause the fridge to continuously run like this? A thermostat or thermister? Need help!!!

Here is your parts breakdown
Model NNT199KA

Could be the thermostat but you should have noticed the unit is colder than usual re: ice cream is a rock.

Check that the condenser fan is running/clean and that the condenser coils are clean. If they are dirty the best way to clean them is with compressed air or a leaf bower. Just roll the unit to an open door and blow the unit clean from back to front. Often this is not possible so you are stuck with a vacuum and brush and often a cut or two.

Remove the evaporator cover in the freezer and check the coils.

If they are heavily iced over you have a defrost problem. Sometimes it can take quite a while before it actually gives a noticeable problem.

Also check if it just has a frost area around the tube from the condenser.
This is an indicator of low freon

Below is some pictures and additional help. Check out #20
http://www.applianceaid.com/refrigerator.html