1: Show up with a garden hose.
2: Narrate it like a nature special.
3: Motion-activated sprinklers.
4: Loom over them and say, "Y'know, the neighbor's dog pisses there."
5: GLITTER. GLITTER EVERYWHERE IN THAT SPOT.
6: Sneak up and yell, "BOO!"
7: Chalk outline of a body.
8: Yell out, "I see you brought someone different this time!" Let each of them wonder which one you're talking to.
9: Speaker + porn music.
10: Put up a sign advertising ticket sales for that time and spot.
11: Leave a pillow with a mint on it for them.
12: Play by play, wrestling style.
13: Mariachi band.