I did an evil thing at the bookshop I was in my local Waterstones, flicking through a book.  I found one of those electric anti theft devices in the book, it's like a square piece of foil bonded to paper.  I had an evil idea.  I palmed the device, and went over to the cookbook section where the obeasts congregate.  I pretended to read a cookbook and casually dropped the device into an obeasts open shopping bag.  10 minutes later she left the shop, and sure enough the alarm went off.  She returned and the security guard asked if she had anything and it said no, so he said walk through again, and the alarm went off again.  The guard asked to look into her bag, and found nothing.  Alarm went off again so they had another look and found the device.  She was red in the face, reeeed a bit and left in a huff.  I was pissing myself laughing.