I'm gonna tell you about the most successful prank I've experienced.
My work had nice stereo speakers setup on space near the ceiling (weird layout). There was a back door to a tiny parking lot that we probably paid more to have (windows and stuff not available to all offices in a shared space).
Fucking leaf blowers show up. They're out there, we can see them. They just won't stop! About an hour in, my buddy complains that they're giving him a headache. Someone agrees they should go away. Another of my friends (to this day, that shithead) starts laughing so hard. "I can't believe nobody noticed!"
He had set the stereo (hooked to a computer) to a youtube video of leaf blowers. The guys with the leaf blowers had been gone for a long time. None of us figured it out. He's a good friend and I still hate him for that. I think I'll slap his baby to get back at him, I'm so mad (still!) (not really, I love him).
I still laugh with anger at how he duped us so hard.
At least once more.