Valerie Bertinelli actually did break her nose on the set, and ended having her first Rhinoplasty.
For the quick shot when Barbara gets hit by the door, a small set wall (6 foot by 6 foot) with just the door in it was rolled in.
In the apartment actor John Putch references Lou Ferrigno from The Incredible Hulk, and Suzanne Somers from Three's Company.