The first trailer that ran in front of The Proposal was none other than Summit Entertaiment's The Twilight Saga: New Moon.Read it for yourself here.
The audience let out a low roar when the Summit logo came up and then you could hear a pin drop with Kristen Stewart and Robert Pattinson on screen. Then when Taylor Lautner appeared sans shirt... well, let's just say there are a lot of fan girls out there. The screaming continued right through the wolf transformation so I tried to focus my hearing on the guy behind me yelling "booo!" to deflect the annoying shrieks.
When The Proposal's final box office numbers for this weekend come in keep Twilight in mind. I wouldn't be surprised if a few million dollars aren't solely the result of Twilighters forking out $10 to see their beloved New Moon trailer on the big screen.
I bet this only applies to select theaters; when the Twilight trailers came out in front of specific movies, somehow they weren't shown at my local theater. Hope that you're a lucky duck who gets to see the NM trailer on the big screen. :-)