In 2000, Google decided to do something special for Valentine's Day, so they asked Ken Perlin, a computer graphics expert in the New York University Department of Computer Science, to create a nice animation. He made a bouncing heart and a lot of special effects (you'll need Java to see it).
Larry and Sergey announced it in a special edition of Google's newsletter: "Just a quick note to let you know about something special that's waiting for you on Google this Valentine's Day weekend. In our long and festive tradition of celebrating holidays, Google is pleased to share with you a special holiday greeting that expresses our love for all Google users."
Because people liked it a lot (maybe because it seemed cute and funny), the bouncing heart returned in 2001. After that, Google stuck only to doodles for Valentine's Day (2003, 2004, 2005).
Last time I saw something Valentine-related at Google? A new logo for Google Checkout. As defined by Wikipedia, "cuteness is a delicate and attractive kind of beauty commonly associated with youth, innocence, and helplessness." Can Google still be cute even if it's not young, innocent or helpless anymore?