damage - Can I break batteries by putting them in the wrong way?

If I put in batteries the wrong way (+ and - sides reversed), is there a risk that I will break them? Or the device? Or start a fire?

In particular, I am talking about rechargeable Ni-MH eneloops and cheap electronic toys for kids, and most of the time not all of the batteries are put in the wrong way, just some of them are reversed (which is probably even worse, right).