Maxis released the first expansion pack, called The Sims 2: University, on March 2, 2005 for PC and December 12, 2005 for Mac. In it, Sims can be sent to college in a new neighborhood type called University. A "Teen" sim sent to the university will become a "Young Adult," a new age group introduced with this expansion, and that sim will become an "Adult" when it graduates or flunks out. Sims that don't attend the university will skip Young Adult and become Adults, as in the original version of the game. A more minor introduction in University is the addition of "influence points" that can be used to influence others to do a certain thing.
The game also introduces zombies and career based rewards which can be "purchased" when you reach a certain level in a specific job.