The Giants started the "ball dude" thing in 1993. It originally was only for men over the age of 60, but now others can do it as well. Krukow and Kuiper love to make fun of these guys. Victor Horwitz (pictured above), the father-in-law of pitching coach Dan Warthen, is the oldest ball dude ever --he's 90 years old.
It looks like it would be fun. Here is a slideshow of a ball dude camp that was held a few weeks ago at AT&T Park.
Below is a clip from Giants Magazine about ball dude camp.
Here is an article written by San Francisco Chronicle writer C.W. Nevius about his experience as a Ball Dude.
Here is another story about an experience of a ball dude. It looks like he really had a good time.
I don't know how one would sign up to be a ball dude, but it looks like fun!