The entire episode backs up one of the lines that Lucy says to Mr. Mooney when he talks about having lots of headaches. She says something along the lines of "You've always had a headache since I first started working here." But when Lucy goes to a department store, she proves she can be more of a headache to salesmen. The best part of the episode is when Lucy is testing dishes that the salesman claims are unbreakable, and she tries to smash it on the edge of a table, making a chunk of the table itself break off.
This is one of my favorite episodes because a lot of the one-liners are callbacks to things that happened or were mentioned earlier in the show.