Step 11: Draw Sid's mouth under the nose using the initial curved lines as guides. Follow the path of the guides as you darken the lines. Use quick, short strokes to draw the top line for a furry texture.
Step 12: Add another curved line under the mouth for Sid's bottom lip. This line should have the same shape as the mouth's bottom line.
Step 13: Inside the mouth, at the top, draw Sid's big buck teeth. The teeth should be different sizes, with the one on the left being bigger.
Step 14: Inside the mouth, at the bottom, draw a series of curved lines that follow the path of the mouth for Sid's bottom teeth. In between the rows of teeth, add a couple of curved lines for the tongue.
Step 15: Use the initial triangle shape as a guide to draw Sid's head. Follow the basic path of the triangle and use quick, short strokes as you darken the lines to give the head a furry texture. The top of the head should bulge up more and form a dome shape, and the fur should wrap around the eyes.