Yep - we've only done it once (so far), and Tristan was little - maybe 3 or 4? We have a really narrow bathroom window that was open a crack, so we hauled out the ladder and dropped Tristan through the window. We said "you are going to be the hero, today!" and as his feet hit the floor, I heard "I don't wanna be hero!!" But, he did go to the front door and open it for us....
I distinctly remember squeezing through a tiny crack in my parents house. The door was blocked by our old chest freezer on the enclosed porch - we never used that door. Apparently, it wasn't ever locked, either! I must have been about 4 when my parents pushed me through onto the freezer. I think I stopped and ate a cookie before I went and opened the door for them, though!