Charlie and Suzie are ranch dogs...each having his/her own special talent to help out on the ranch. Charlie's happens to be more of the slower variety of helping than Suzie. They would be two easy characters to compare with their work at the ranch.
I would consider using the illustrations as part of a study on Dian deGroat, illustrator of We Gather Together...Now Please Get Lost!
, Liar, Liar, Pants on Fire
, and other Gilbert books.