It's a Dad, Dad World S01 E01

Dr. Bindlebeep's parents, Lester and Louise receive a visit, from Arthur, Norma, and the kids. Since Arthur is his father's son, he goes back to acting like it. Unknown to Dr. Bindlebeep, his father is in very good shape, better than him. He exercises regularly to stay like this. They play touch football, and Lester is injured. Arthur was acting like the son, but roles have switched when his father begins taking over the role of son, from his injury.