The problem with pizza was hinted by Lacuna in CD.  It's not firm at all, but she seemed rather distressed that they were eating it as if it could have some bad ramifications.  (they could be imagined, or the ramifications might only be important to someone with Lacuna's particular quirks, but they could be significant too)

I have thought that Lacuna was apposed to pizza and candy because she was a tooth fairy and apposed to any junk food, though I don't know of any confirmation of my guess.

Edit:  I thought the Lacuna=Tooth Faerie idea was so cool I exercised my curator powers to split that part of the topic off to make this dedicated topic for it.  This way others that aren't following the older topic are more likely to be exposed to it, and later it can be stored in the DFRC as a stand alone theory.  ^-Serack

Edit 2:  Jim said here that he kinda included who Lacuna is into her name.  Jump down to this post to see how this discussion has already covered this. ^-Serack