Many thanks to Michaela Conlin from Bones for demonstrating the perils of zipper-front dresses:

That thing has more peaks and valleys than the Appalachians. The zipper makes the dress lay really oddly on her, and then when she sits down, it’ll do that thing where it pops up in one giant lumpy hill, and THAT will lead to awkward polterpackage jokes like, “Is that your zipper getting kinked or are you just happy to see me?” and “BONES, eh, nudge-nudge,” and “Here, Tommy Lee, I have a boat you can steer with that thing,” and that will just be really awkward for everyone because NOBODY wants to encourage that level of hackyness.