An easy way to implement small pets

[Grobble]

I know at least a few of you want tameable critters. I though of a way to implement them without adding a whole new system.
A buildable glass and/or metal container that you can put small animals into. Once a critter is inside, it could periodically trigger an event, like the natural landmarks do and give a small amount of exp.
You could prompt for a name once the critter is in place, which would display when the container is opened.
If you want to get a little fancier, you could have the critter require feeding similar to silkworms.