An unlikely sign

I would never have guessed there was a sign like this somewhere. It makes sense that you wouldn't want balloons on the SkyTrain (as they'd get caught in the doors, I guess), but it still struck me as a bit unusual to have a sign dedicated to this particular problem. You wouldn't want tigers on the SkyTrain either, but would you have a sign that says "No Tiger"?

Maybe balloons on the SkyTrain were a big problem before the signs?

(note: this actually might put a cramp in our style, too - Sam's been eyeing up a nice Hello Kitty balloon they sell at a downtown mall, but if we can't bring it on the SkyTrain, then it's not convenient for us to bring back to our place -- guess we'll have to find a more local Hello Kitty balloon vendor!)