What are some fun places to go on a rainy day in san francisco?

Me and my girlfriend had a date planned for today in san francisco (it was going to be an all-day date)... originally planning on the ZOO... but now it's supposed to be "stormy" all day. So change of plans. Any good /fun places to go in san fran that might be indoors? Or just reallyt fun to do while on a rainy day? I was thinking the Exploratorium... but I need more ideas heh. HELP! :)