In The Great Gatsby, George Wilson is a minor character who acts as a foil--a character who has character traits that are the opposite of another character. Mr. Gatz is a flat character, a personage who has only one or two personality traits and does not change throughout the narrative.
George Wilson is a product of the wasteland of the Valley of Ashes, just as Tom Buchanan is a product of the rich world of East Egg and New York City. George is a man that Nick describes as
...a blonde, spiritless man, anemic, and faintly handsome. When he saw us … hope sprang into his light blue eyes” (Ch.2)
and he describes Tom Buchanan in a different manner:
...a sturdy, straw-haired man of thirty with a rather hard mouth and a supercilious manner. Two shining, arrogant eyes had...dominance over his face....His speaking voice, a gruff husky tenor...[has] a touch of paternal contempt in it. (Ch.1)
George loves his wife Myrtle deeply; when she is killed, he is deeply changed emotionally--"deranged by grief." In fact, George grows deeply depressed. Reacting differently, Tom is angry that someone could run Myrtle down in such a cruel manner. But, while George tries to avenge Myrtle's death, Tom easily discards the memory of Myrtle and, instead, helps Daisy escape her culpability for her crime by giving Wilson Gatsby's name so he thinks that Jay Gatsby ran over his wife. Certainly, Tom and Daisy are rightfully called "careless people" by Nick.
As a foil to Tom Buchanan, George Wilson represents the lower classes trapped in their poverty, while Tom represents the amoral upper class, concerned only with their own pleasure.
Mr. Gatz, Jay Gatsby's father, is a flat character, a personage who remains the same throughout the narrative, but he does serve a purpose. He arrives at Gatsby's house in order to bury his son. Mr. Gatz is extremely proud of his son, Jimmy Gatz, as he calls Gatsby. He walks proudly up and down the hallways, impressed with the size and opulence of the house. He pulls out pictures, proudly displaying them, saying,
"He knew he had a big future in front of him. And ever since he made a success he was very generous with me."
Mr. Gatz also displays schedules that Jimmy wrote out years ago as a demonstration of how his son was destined to succeed. Both he and Nick attend Gatsby's funeral. There Nick looks anxiously for other cars, as does Mr. Gatz, whose appearance in the narrative reveals the falseness of Gatsby's life.