Decorate cookies. For eyes, use tip 3 and full-strength white icing to pipe eyeballs. Pat smooth with finger dipped in cornstarch. Use tip 1 and full-strength black icing to outline eyes. Use tip 2 and full-strength blue icing to pipe iris. Pat smooth with finger dipped in cornstarch. Use tip 2 and full-strength black icing to pipe pupil. Pat smooth with finger dipped in cornstarch.
For teeth and eyelashes, use tip 1 and full-strength black icing to outline teeth and to pipe eyelashes.
For mouth, use tip 1 to and full-strength red icing to pipe mouth, smile creases and mark beneath teeth. Let set 1 to 2 hours.