We thought you'd like to see the character designs for Anna and Elsa's casual clothes, including some unused options:
Character art is by Ami Thompson, the fashion is by Griselda Sastrawinata, and the alternate designs for Anna's shirt are by Cory Loftis. As you can see, an alternate idea for Anna's shirt referenced her propensity for punching princes, while Elsa might have ended up in a stripey sweater with Marshmallow on the front.
Also, it turns out someone else had the same idea for the "milkshake" joke before we did: