I learned this in my fondant class. I baked and cooled 3-layer cakes, dowel rod all tiers except top tier.
I positioned the middle tier on the base tier, centering exactly (but first cut it, turned and put it back on). Repeat with the top tier. Prepare for covering with rolled fondant by lightly icing with butter cream. Cover top and bottom layers with white fondant. Smooth with fondant smoother. Cut off excess with knife.
Cover the middle cake with green fondant. Save some on a side for stars, and smooth with fondant smother. Color fondant with black Wilton color and cut it in small pieces, glue it with piping gel.
Make one black fondant bow. Attach in center of ribbon with piping gel. With white butter cream I made some pearls with tip 10. For the stars get the reserved green fondant and use a star-cookie cutter and create a few different sizes. Use wire to put it on top and there’s your craziest Topsy Turvy birthday cake.