I was so confused. I thought maybe the sandals only came in taxi yellow with black and white checkerboard patterns on them. Or maybe the cab was held together with straps. Or maybe "keen" was just being used as another way to say "neat". After Googling all the related topics, I now see just how significant this whole sub-topic was. Thanks for sharing.

I do not like them on a trike.
I do not like them on a bike.
I do not like them in a cab.
I do not like them in the lab.
I would not wear shoes, "Keen," you call
I would not wear them one and all.