Another characteristic of an incandescent lamp is it changes resistance with temperature (of the filament, not ambient). So If I recall correctly a typical 120V bulb is approximately 1/6 th the resistance when "cold" (i.e. measured with an ohmmeter) that when it is at the normal 120V operating point.
So the resistance does change but not magical. You can also look up the temperature coefficient of resistance of tungsten to get an idea of the change.