Department Store Reopening
If you talk to the mouse at the base of the escalators you'll get some foreshadowing about what is to come.
Don't buy anything for Paula for now. Make sure that any items you want to have access to are moved over to either Ness or Jeff's inventory. And definitely if Paula has the Franklin Badge or the Pencil Eraser make sure to give it to Ness or Jeff. You will need them.
There is one of the shady salesmen in a back room on the second floor that can sell you some Big Bottle Rockets, make sure to stock up on those for Jeff.