Facial proportion exaggerations will change the entire feel of a face, and should when designing good characters! (you can use techniques like drawing one image then copying the original 2 times and liquify and warp 2 more in photoshop to push it). Your placement of the structural lines of the head will change the character design age and expectations of beauty stereotypes and personality expectations.
Cynthia Cooper- Using Liquefy and the transform tool in Photoshop to exaggerate facial proportions.
Brittany Zerkle - Proportion shift on Female Character head shows a shift in age.
Kate Flynn - Proportion shift in the Male Character Design shows a smarter character with more brain room and a hunkier character with more jaw.
Josh Schimke - Proportion Shift on Alien head design shows friendly, lonely and nerdy characters. Use the thirds rule in the design giving precedence to the top or the bottom or the width of the design.