TL;DR - Dead body in a body bag started moving around and brushed against my leg. I was so terrified and shocked I couldn't scream.
When I was in my teenage years, my Step Father owned a business that transported dead bodies from the death scene to the local morgue. The coroner (in our county anyway) simply declared the body dead and made a death certificate. EMTs are meant to deal with people who probably aren't going to die. Firemen and police don't move dead bodies, so that left my Step Dad and his business. We had a drug overdose, young pretty woman probably 28 years old tops. She died alone in her house, surrounded by clutter and what not. We toss her in the body bag, seal it up, then I start talking to the coroner. Without me knowing, the bag looks like the body is bending at the waist, ever so slightly. I knew about gases escaping creating a wheezing sound, or like the person was breathing, but bodily movement was something I've only heard of in passing. The now wiggling body (there was no speed or persistence to the wriggling, it was slow and deliberate) barely touched the back of my calf. I turned around and saw this scene I am describing. I still moved dead bodies for years after that. The work paid well and I had no problem with the breath.