Sometimes I go to the third park bench on the right past the main trail entrance, and I just sit there with a birthday cake and candles. You get a good laugh at the first reaction of people walking by, but it’s that second and third lap when they realize you haven’t taken a bite yet that is really funny. Try to time it just right, because this prank won’t work on the hippy crowd. They’re either too high to notice, or they’ll just stop and ask you something stupid like “Who’s birthday is it mannnn”