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.
"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!"