Step 15: Darken the angled line on the left side of the body for the first arm. Add another curved line next to it to make the shape of the arm thicker. Inside the rectangle at the bottom, draw a smaller rectangle for the cuff on the glove. Darken the rectangle for the rest of the hand but make the side curvier. Draw a series of short, curved lines along the bottom for Beast Boy's folded fingers.
Step 16: Draw a short, curved line under the head for the costume's collar. Along the bottom of the torso, to the right of the hand, draw a couple of small, rectangular shapes for Beast Boy's belt. Don't overlap the shape of the hand as you draw the belt. To the right, draw a small circle for the belt buckle. Along the right edge of the torso, draw another couple of short, thin, rectangular shapes for the rest of the belt.
Step 17: Darken the sides of the initial shape in the middle to create Beast Boy's torso. Don't overlap the hand or the belt as you draw the torso. Darken the bottom edge too. Add a couple of long, curved, vertical lines inside the torso for the design on this Teen Titans Go! character's costume.
Step 18: Draw the visible part of Beast Boy's other hand inside the small shape on the right side of the belt. Make the top part angled for the glove and the bottom part curved for the folded fingers. Darken the guide on top for the arm. Draw a second line next to it to make the arm thicker.
Step 19: Draw a small, angled line above the square-like shape on the lower, right side for the shoe's tongue. Add a curved shape near the top edge of the initial square for the fastening section of the shoe. Across the middle of the shape, draw an angled line for the top part of the shoe's sole. Darken the bottom of the shape to finish the sole. Darken the guide line at the top for the leg. Draw a parallel line to the right to make the shape of the leg thicker.
Step 20: On top of the small rectangle on the lower, right side, draw a small, angled line for the shoe's tongue. To the right, draw a small, curved, rectangular shape for the fastening section on Beast Boy's shoe. Darken the side of the shape. Draw an angled line across the shape for the top edge of the shoe's sole. Make the sides of the shape curvier. Darken the bottom edge to complete the sole. Darken the guide line at the top for the leg. Add a parallel line next to it to make the leg thicker.