I played on the Project 1999 with a few friends several months ago, the population has really grown.
When we played I found that I could set my pet anywhere I wanted, leave him there, he'd aggro aggressive mobs, and was so strong he could solo them because he was up to 4 levels higher than myself, and I got full exp.
So me and a friend made two mages, and did this by setting our pets on patrol paths of various hostile undeads in a handful of zones, and would leave our toons standing next to guards all night while our pets killed and pillaged everything and leveled for us while we were sleeping.
It was a lot of fun, but then I became famous when everyone on the forums went apeshit because I would go up like 3-5 levels a day or more while not even actually playing the game. Then they made drastic changes to the Magician class and how pet and player could get exp. They really made it shitty for Mags after that, really gay.
We did this for a few weeks, maybe a month or more. I gave my account to a friend of mine who actually uses it now. Now it's 50, geared to hell, no idea if he's still playing it or not now.