If you want to know what Anna and Elsa did please read the story: It's Time for Anna and Elsa's Sister Day. The story is in the Disney Princess articles section.

It would have been great if it weren't for the nakedness. Anna may be silly, but that just doesn't seem like something she would want to do. Randomly taking your clothes off isn't funny in my eyes, it's just plain weird.

^^ Why not just have her cover herself with a napkin?

I guess a napkin would have been better. I didn't think of that when I was writing the story. At least Anna and Elsa were in their kingdom so nobody saw them.