It's Cal's (presumably now annual) School Haas Rock event, in which the Bears play really early in the day and a bunch of school age children come to make an almighty ruckus! The early start time isn't exactly great for MY ability to watch the game (and really, what's more important than that!) but it's a cool event for the kids and I get the sense that the players and coaches really enjoy it as well.
UC Riverside is this year's opponent. The Highlanders were a middle-of-the-pack team in the Big West last year, but have gotten off to a good start this year with a pair of easy wins over Fresno State and San Diego State.