Do billboards work?
My colleague Jay Levinson taught me that the two best words to have on a billboard are, "next exit." I have serious doubts that you can cost-effectively sell an item that isn't a "right now" purchase from a billboard, though. I'm have no doubts at all that hospitals have no business whatsoever running ads on billboards. "Oh, George, you've been thinking of having heart surgery--look at this great ad from Memorial Hospital!"
So, yes, it's funny and even memorable. But is it selling muffins or a particular brand of muffins? If I got a muffin craving from this ad, would I pay extra for these particular muffins?