I know its theoretically impossible to reach 0kelvin, but if we were to pretend it had been achieved, is there any phenomenons predicted to happen?

another question on the topic that has me a bit confused. 0 kelvin is -273.15c, where does the .15 fit into the kelvin scale? eg 0 kelvin must be -273.15 (most accurate measurement I'm aware of) so does that make 1 kelvin -273.15 or -273.00?