The anamated GIF image on the right shows the variable brightness effect you can get with regular incandescent series string Christmas lights plugged into a specially wired pair of extension cord outlets, the outlets wired in series. You can add more sets to the eight shown, and you can get even more variety of brightness levels. Just be sure the amount of strings are equal on both outlets. You may need to swap a few strings from one side to the other and others the opposite way to get a more even distribution of brightness. All the bulbs will run at reduced brightness than normal, but this will dramatically increase bulb life, and will still be plenty bright enough. The time sequence will be completely random in a real setup.
And during the off season, you can use this set of plugs to test old radios using the current limited lightbulb setup. Radio plugs into one of the sockets, a table lamp with a 100W lightbulb in the other. If the radio has a serious overcurrent problem (like a short), the bulb will light up brightly. This can save blowing a power transformer.