It went kinda like this.
Yesterday, I finished work early, and my boss was generous enough to give me the rest of the day off. I felt like doing something unusual and more outdoors-y than I'd normally do, so I went to the zoo. It had been YEARS since I'd last visited one.
I was surprised to find that apparently, my town's zoo now had lions. Seems they'd been caught in the wild and were going to be sold off when the guys at the IBAMA (Brazil's equivalent to the Environment Protection Agency or whatever the heck you guys have) busted the whole operation. Some of them were donated to the local zoo.
In any case, I'd never seen a lion in the flesh before. There were a bunch of children around the cage who were pretty fascinated with it.
I have no idea why, but the lion began to growl. Some of the children got scared and ran behind their respective parents. One of them began to cry. The lion began to get more aggitated, and started pacing back and forth in its cage. Which did precious little to calm the kids. Eventually, it roared and began trying to reach its claw out of the cage. It was pretty big, so the claw actually almost extended all the way to the spectator area. It roared again. Somebody called for the handlers.
At this point, I began to stare into its eyes and roared right back.
It wasn't as loud, of course - I don't have a lion's lungs - but it was deep, and it echoed. There was silence immediately afterwards, and I fixed my glare into the lion's eyes. We began the world's strangest staring contest. It began to arch its back as if ready to pounce at me. It showed its teeth, growling in the back of its throat. I did the same out of some strange, animalistic reaction, and took a step forward. The lion took a step back, and I took another step forward. It began to growl more loudly, and I roared at it again. The lion relaxed and stalked away, lying down with its neck towards me.
...when I came to, everybody was staring, and with good reason. The handlers said they'd seen other people manage to tame animals when they were aggravated before, but this was the first time they'd seen this particular method.