Tony Bennett may have left his heart here 50 years ago, but San Franciscans only wanted to leave their hearts for the penguins at the California Academy of Sciences on Monday afternoon.
In what has undoubtedly become the Golden Gate Park's Most Adorable Tradition since baby bison, each year, fans of the waddling birds pen their own Valentine's Day cards -- on non-toxic cardboard, of course -- and then distribute the gifts to the penguin colony.
And the arts and crafts project comes in handy, too. Biologist Brooke Weinstein told NBC news that the penguins use the cards to build their own nests.
Take a look at darling images from this year's event below, and click over to Cal Academy's live penguin stream to get even more of your tuxedoed fix: