My current Legacy family celebrated by throwing a huge party in Central Park; the whole town was invited. It started promptly at 11 AM on a Saturday when everyone (including Dad) was free from work and school. I'd edited Central Park earlier to provide things for the party, and the all-new Central Park had a huge buffet table area, a place for running around in the sprinklers (the lucky father's a gardener), and the expensive stereo for dancing.
About 10 Sims were invited, and about 30 showed up. In any case; the party was a roof raiser and all of the Sims had a good time. Unfortunately, since I was mostly playing around with my legacy family, I did not save the game file.
On a side note: When I returned to playing the game normally, on Saturday night, the Mother gave birth to a bouncing baby boy. Coincidence, much?
Did anyone else do anything like this? Is anyone planning to? Was anyone (more or less) inspired by this?