A couple times throughout the series, Bella asks whoever is accompanying her at the time for a "human moment", at which time she either rests, eats, or goes into the bathroom.
While I imagine some of these moments are simply to apply/reapply makeup, take a shower, brush her teeth, etc., many others would be so she could use the toilet.
And therein lies the mystery for me. Meyer's vampires have super strength, resilience, sight, hearing, and smell. It is demonstrated many times that they can hear each other whispering throughout the entire house. Unless I am missing something, this means that every time Bella sits on the toilet, there is an entire household of vampires hearing every sound she makes.
In addition, with their super-noses, they would be smelling whatever she did long after she left the bathroom.
I have to wonder what the vampires do when this happens, or if Bella even knows. That awkward moment when...
Anyway, that's it for now... but don't worry I have lots more. I'll put them up eventually. Let me know if you have something you want me to mention, or if I should stop because these are boring.
Next up: I don't know yet; probably BLOOD.