After many trials, found a good marshmallow fondant recipe and practiced rolling it out and covering boxes, as this Toy Story Birthday Cake Design was my first attempt at fondant cake. Put plastic support tubes into the bottom cake to support the bed on top of it. Used molded Rice Krispie Treats for the pillows. Was going to attach head and footboards of molded chocolate (made in a heart-shaped mold) but made them too thick the first time and too thin the second time, so we just left them off.
Practice way ahead of time if you haven’t done the fondant before. If you are making your white cake from scratch, DON’T use the recipe listed in the Wilton cake information. It was terrible. Thankfully, I tried it a couple weeks ahead of time. Allow for lots of time if it’s your first attempt so you can practice!