The only Frozen party they have is the dessert party at Epcot, and that's something entirely different.I just found this online = In 1995 it was a small scale party and not exclusive for a special ticket, it was really not until 2002 that it became park wide with all the extras. Disney only pushed it to a large scale when they realized they were losing a lot of money to Universal. I dont think they excluded people without tickets at that time. Those people just had wrist bands & could get into special designated parts of the park. I remember going when Frozen had a special party & they just had it fenced off. But, the regular guests & passholders did not have to leave the park like they do now. When I have time I will call DWorld and ask them. Im guessing most will not know because the people that answer the phone are very young and probably dont know when it started or any of the details from the 90's. But, I have learned my lesson the hard way. We are going today and it is a none party day and we can stay in the park until 11 pm. Only 2 days this week that passholders can stay late. We are blocked after Wed for Xmas & cant go back until January.
Or perhaps you are thinking of the Frozen characters doing the castle lighting in the MK, which is done every night during the holiday season, and is not part of any special event. Just part of the daily park entertainment.
My single best piece of advice to you is to consider going to the MK on a party day in spite of the earlier close. The later closing days are much busier because so many people try to avoid the earlier closing days.