Hah I dont think it was Dennis, though I didn't really look I was watching LBG to much and the truck was pretty packed.
Regarding the powerups the only one that I got during the level I played was the jetpack, it didn't look like they were letting anyone mess around with the level creation part of LBG. They also didn't have many stickers unlocked so I had limited experience with that.
Most of the level mechanics centered on grabbing things and moving them around, or grabbing things and having them launch u into other things, though I did get to ride the skateboard.
Also, it didn't seem to be running very smooth, I understand it is a demo but I hope they jack the framerate up b4 release otherwise it will be very disappointing.