You lie down on a rock as the two miffed zookeepers leave the room. You go through what just happened in your head.
"I'm a tiger," you think to yourself. "I don't want to be a tiger, but I'm a tiger." You think for a moment. "The guy who left with whatsherface over there used to be a tiger, but now he's human, which isn't exactly lighting up his day either, not only that, the poor schmoe has to clean up after me and a bunch of other animals...hah...sucker."
Then it occurs to you...he WAS irked about being human. Maybe...just maybe....you might have a plan.
The rest of the night you busy yourself with messing up the cage a bit. The next day the ex-tiger comes in wearing a zookeeper's uniform and a deep scowl. You dive playfully into your pool and try and look like you're enjoying yourself. His scowl deepens.
The rest of the week you make repete this ritual. Mess up the cage at night, enjoy yourself during the day. There are a few moments when you start to forget that you used to be human, or what your name was, or your family. At times like these you find it helpful to sing old familiar songs in your head or recite old limmericks or nursery rhymes. Each time the ex-tiger looks angrier and angrier.
Finally, maybe a month into your situation, he calls you over.
"Look, pal, I know what you're doing. You're trying to get me to miss being a tiger so much that I'll trade places with you and let you free. Well it's working, this biped stuff is killing me. I can't figure out the microwave, the TV, the DVD player or the appeal of half of the popular music today. So, if you'll agree, I'll just switch us back."
It worked...