>>22565357I'd wager most Whimsicott are running 252 HP/252 (S)DEF/4 SPE. There might be exceptions, but generally you ought to be able to speedcreep that with relative ease, either with a genie, another Whimsicott, or maybe even a Sableye?
As much as I love it, I have to admit Whimsicott's stats are kind of shit, and it doesn't usually carry Synthesis (if it even learns it) like Sableye carries Recover. It definitely needs the defensive investment to do what it does effectively. With that in mind, I'd say it's a safe bet that the fastest Whimsy you'll find is probably running 4SPE if it's not specifically geared to beat out other Pranksters.