Yes, I have been involved in a PFY pranking. The PFY concerned was one of the suit, tie and briefcase type (opposed to the rest of us in jeans and t-shirt) and he was very proud of his company issue Rover 214 (which, in his mind, was very sporty). He'd turn up with a glint in his eye and a snap in his heel, the epitome of bright eyed and bushy tailed. Where the rest of us just grabbed a toolkit (necessary screwdrivers, install CDs, Floppys, spares and so forth), he'd carefully decant the bits he needed into his briefcase (a wholly unsuitable receptacle for the job). Had it been me, I'd have opened that case in a slovenly, can't be arsed, listery kind of fashion - but he always opened his case quickly and smartly like a door to door salesman.
We thought it'd be a damn good idea to booby trap his case and then send him out on a job with a tame, and thoroughly briefed, client. The booby trapping consisted of strong elastic rigged to snap his case shut again just as quickly as he opened it, and the briefcase then filled with packing chips. Nice.
A few hours later the client (Hello, Nige!) rang with a fit of the giggles. The plan had gone off without a hitch. PFY had turned up smartly, smarmed his way up to the supposedly ailing computer and (before checking to see if anything was really wrong with it - and nothing was) whipped open his briefcase- which snapped shut again in a blast of packing chips.
We didn't see the briefcase very often afterwards.