I was on line to show my ID (not actually necessary to get on a plane, by the way) at Phoenix's Sky Harbor Airport the other day when the woman in front of me pulled out a small container of strawberry yogurt and asked the blue-shirted TSA representative (I miss those maroon sweater-vests), "Can I bring this on the plane?" The TSA agent inspected the yogurt container carefully, and then reported the sad news: "You can't. It's a gel."
A gel? Yogurt is yogurt. People don't eat gels. The woman didn't fight, however. She handed over the contraband yogurt, and the TSA scored another victory against reason.