Mr. Pignati, Lorraine and John all seem to create a second family unit through their friendship and adventures together. Lorraine and John are teenagers who have difficulty at home with parents. John's dad is very controlling and Lorraine's mom criticizes her for just about everything she does to the way she looks. Mr. Pignati is a lonely man whose wife has died, but he tells the kids that she's just on vacation. This seems to be how Mr. Pignati deals with the death of his wife, but it makes the teenagers feel pity and compassion for him. Mr. Pignati acts like a father-figure by giving money to Lorraine so she can buy nylons, but because of his grieving mindset, there are times that Mr. Pignati seems like the child and the teenagers are the adults. Therefore, Mr. Pignati fills the void of a loving and fun parental figure in the teens' lives and they fill his empty house with laughter as if they were his kids.
They become friends because it all started as a joke that they played with other friends. Then it continued on when they went on adventures and does not end even after he dies.