Those guys really don't mess around.
The other night, as we were wrapping on a short that I Art Directed, I parked the car a wee bit too close to some cacti on the side of the road. As I got into the passenger side later, my leg brushed up against one, and I said, "Ouch! Cactus!", but then it was pretty much over.
But! The next day in the car (we were on the way to see Take Shelter, which I highly recommend. Just great!) I wiggled in my seat a bit, and Youch!!! I said, "Aaaaaaiigh!!!, I think there's a cactus spine in my leg!". But I couldn't do anything about it. (Darn you, skinny jeans.) I had to run into the bathroom and take off my pants. I found the perpetrators - two of those hair-looking spines had caught in my jeans the night before, and had laid low until I wiggled. It took a few minutes to pry them out.
Nasty little buggers.