Just after Tim looks at Jill and the boys through the window in the backyard a microphone is visible when he speaks to Wilson.
While Tim and Al are shopping in the women's department; Al is asked if he prefers big women. He says that his mother "was a big woman". Al's mother doesn't die until the last season.
Jill's Birthday, her birthday is set during the winter months because the characters are wearing coats. In Jill's Surprise Party (#5.4) Jill is going to see her cousin about the piano, Jill is wearing a short outfit with no coat, it seems to maybe her birthday is set during the spring or summer months.