Nice work! I first came across this concept a few years back when someone posted an instructable which I believe he was building a Magic mirror for his daughter [1]. I re-implemented the idea but with a spooky tone, ie. it is framed as a regular mirror in the living room and when a guest stares at it long enough, something spooky jumps into the view. This was done using a VGA monitor, camera and a netbox pc. It was a fun project. If I were to go at it again, I would just use a cheap android tablet solely based on price, simplicity and power consumption. Will also make it useful this time with display of data that interests me than a novelty toy.
Yes you can and there are other tricks too. However, since its not the default behavior and given that most people don't realize it when setting up forwarding, it can be considered a bug.
I think it has to do with that post where someone missed out on important legal mails because gmail chose to only forward those mails that passed their spam test.
[1] http://www.instructables.com/id/The-Magic-Mirror/