You shouldn't make fun of someone's parents.
Jack comes over to William's house for the first time where he is greeted by William's dad who is in a wheelchair.
Jack wants to tell William what he thinks of William's dad.
Jack tells William that he is delighted to meet his father and hopes to get to know him more.
"Jack turns to William and laughingly says ""wow your father is a cripple? I never knew""."
William is happy to have introduced the two of them and is all smiles.
Both William and his father are hurt, embarrassed and horrified at Jack's callousness.