In advance: Make fondant hamburger, spatula, candle, and hat. Combine 2 teaspoons of Gum-Tex with 24 oz. of fondant and tint as follows: 2 oz. each: navy blue, black, tan (for bun), reddish brown (for burger), Leaf Green (for lettuce), gray (use a small amount of black), light blue; tint 1 oz. yellow. Reserve 6 oz. white. Roll out fondant 1/8 in. thick on cornstarch-dusted surface. Using patterns, cut entire hat and hamburger/spatula/candle in white to use as base; cut color sections using patterns and attach to white base with damp brush. Marbleize yellow and brown fondant from burger; roll out 1/8 in. thick and cut flame shape. Let dry.
Bake and cool cake. Trim off left hand and open area on left side of body; leave sleeve. Ice sides and background areas smooth. Pipe in tip 3 SpongeBob spots (smooth with finger dipped in cornstarch). Pipe tip 3 whites of eyes, irises, pupils, tongue, mouth and teeth (smooth with finger dipped in cornstarch). Outline body, face and shoes with tip 3. Cover face, right arm, legs and shoes with tip 16 stars. Using tip 3, pipe string eyelashes, stripes on socks and belt, pipe in tie and add dot freckles. Position spatula; attach hamburger and candle with dots of icing.
Curve lollipop stick to make arm holding spatula and cover with fondant; insert in cake. Cut hand using pattern and white fondant; position on cake. Outline hand and arm with tip 3 and cover with tip 16 stars. To support hat, insert 2 lollipop sticks in top of head; one extended 1 in., the other 2 in. Position hat on sticks, attaching with thinned fondant adhesive; outline top and pipe anchor with tip 3. Pipe tip 21 shell bottom border.
*Combine SpongeBob SquarePants Yellow, Blue and Brown for green outlines on SpongeBob. Combine Royal Blue, Black and Violet for navy hat brim shown. Combine Brown with Orange for tan bun shown. Combine Red with Brown for reddish brown hamburger shown.