Bake your favorite 2-layer 13 x 9 cake recipe or mix following recipe instructions. Cool in pan on wire rack 10 minutes. Remove from pan and cool completely. Bake and cool your favorite pound cake recipe or mix in bear pan, following pan instructions.
Arrange 13 x 9 cake on foil-wrapped cake board. Spatula ice cake with yellow buttercream. Decorate tip 3 dots on top and sides of cake in assorted colors buttercream. Use tip 8 to decorate alternating colors ball bottom border. Using 8 in. separator plate, mark cake top. If needed, cut hidden pillars; center and insert 4 pillars in sheet cake over marked area where plate feet imprinted.
Arrange bear cake on separator plate, attaching with icing. Ice inside of ears and bottoms of feet smooth with spatula. Decorate tip 3 nose, eyes and mouth (smooth areas with finger dipped in cornstarch). Add tip 16 chocolate buttercream star "fur."
Carefully place feet of separator plate with bear into hidden pillars. Insert balloons into bear's paw.