Willy Jr. is Jeff Winger's half brother to whom he is introduced on Thanksgiving after arranging a reunion with his estranged father. Although he is named after their father William Winger, he is considered a disappointment due to his relative immaturity. Physically and personality wise he is on the surface the opposite of his brother; shorter in stature as well as outwardly emotional in state of arrested development. His first appearance is in the Season Four episode "Cooperative Escapism in Familial Relations". He is portrayed by actor/comedian Adam DeVine.
After William Winger lets Jeff into the house and establishes ground rules for the Thanksgiving dinner, Willy Jr. awkwardly greets his half-brother from the stairway. Willy immediatley becomes jealous of him claiming that Jeff is the "Schwarzenegger" to his "DeVito". As Jeff and William continue to bond, Willy Jr. and Britta (who had invited herself to the reunion) sets the table for dinner. Angry at how close the two seem to be getting, he throws a bread roll at his father. After being yelled at by William, he runs off upset with Britta close behind offering to help by therapizing him. William explains that Willy's mother died twenty years ago and he still hasn't gotten over it. He goes on to add that despite his own best efforts Willy hasn't matured or grown up much at all. Stinging from his father's criticisms, Willy Jr. hides inside Jeff's Lexus. During an after dinner conversation, William mentions to Jeff how leaving him and his mother helped turn him into a stronger, well-adjusted man.
Angered by the thoughtless comment, Jeff storms out of the house and drives away. While on the road, Willy reveals he had been hiding in the back seat. He pleads with Jeff to be taught how to be like him. He knows William hates him and wants to become as cold and aloof as Jeff so their father will like him again. Jeff tells him he should instead learn to not be concerned what their dad thinks as he is a terrible father. Willy then makes Jeff realize that by not expressing these emotions to William it's the same as letting their father off the hook for being a bad parent. He turns the car around and takes them back to the house where he confronts William. As Willy and Britta watch, Jeff counters Williams earlier assertion and lets him know how badly his abandonment of him affected him all these years. Afterwards, Willy Jr. finds Jeff and Britta inside the Lexus before they leave. He thanks his brother for standing up to their father and saying what he couldn't say. He then climbs in through the Lexus' open window and embraces Jeff in a hug.