I was cleaning out my desk draw the other day and came across a bunch of batteries. I have a pretty good collection of rechargeables so I threw a few in the charger and plugged it in. After about 20 minutes, I heard a little pop-sizzle-whistle noise. This is what I found:

.
Didn't see it? Look al ittle closer:

You might notice a little foamy goodness leeching out of the
non-rechargeable battery.
Oooops! I wasn't trying to be cheap, I am just becoming senile.