To fart, then walk past an unsuspecting victim very close, preferably while in a small room (copy room, broom closet, etc...) and say "fly by". After a second or 2 the victim will know what you mean. You can even make plane noises on the approach and retreat for added effect.
Predator: Fly by!
Victim: What the hell? (breath in) awwwwwwwwww man!
Predator: Ha ha ha
When an person/animal is lying down & you run up to them, fart on their head, & leave the room.
"You should have seen the look on my cats face when I did a fly-by on him last night! He now twitches & I'm waiting for his left eyebrow to grow back! Priceless!"
"Dude, I did a fly-by on my mom yesterday! She didn't find it as funny as I did. Anyways, I can't come over, I'm grounded!"