Trim off necktie, right arm and heel areas from cake. Ice sides and background areas smooth. Using buttercream, outline SpongeBob, spots, facial features, arm, hand, trunks, legs and feet with tip 3; outline tongue with tip 4. Pipe in tip 3 spots, eyes, irises, pupils, inside of mouth, teeth, cuff on sleeve; pipe in tongue with tip 4 (smooth all with finger dipped in cornstarch). Cover head, trunks, legs, arm and sleeve with tip 16 stars. Pipe tip 3 drawstring bow on trunks and string eyelashes. Roll out reserved brown and red fondant 1/8 in. thick. Using pattern, cut surfboard tip in brown and a 7/8 in. wide red strip to fit. Attach strip with damp brush. Outline flowers with royal icing and tip 2; pipe in using tip 3 and thinned royal icing. Pipe tip 21 C-motion bottom border. Insert surfboard body into cake side; position surfboard tip behind right leg and fin under surfboard; support surfboard body with marshmallows.