Panel 1: Dee tells Liz that since the Miracle Dress fits her like a glove, she was meant to wear it. Is this a surprise? No, it is not.
Panel 2: What is equally unsurprising is her realzation that Jim might have some input into the matter. God knows the only time she or Mike visit is when they want something.
Panel 3: Her belief that his memory faded is predictable. After all, she's hoping he forgot he ever had a harmonica.
Panel 4: The least surprising thing of all is the glurgy, fridge-quality payoff line about it seeming like yesterday. The only people who will be floored by this are the Kool-Aid Drinkers.
ETA: As howtheduck said on his blog, the horrified look on Jim's face comes from his assuming that Liz just got married and they're informing him after the fact.