There's some trick Pikachu can do with this in vBrawl called the Pikaslide, and it usually is dtilt ->fsmash (works with dsmash) and Pikachu slides back a good bit - useful for Pikachu, as one can be fsmashing someone trying to punish dtilt (or just making dtilt safer in general on shield).
I don't know if it's something about Minus, or if this property exists on other characters in vBrawl as well, but I don't believe it does (or else you may have just found a new trick for Peach in Brawl - if it works in Brawl, you or I can go to the SWF Peach boards (I'll credit you if you don't care to do it) and post in the "Ask a Question, Get an Answer" if it's well-known that Peach can Pikaslide and the Pikachus just never let the technique take a less character specific name). The reason I don't think it is in Brawl is because Pikachu is thought to be able to do it because of the unique dtilt animation.
Nice find either way though. At worst, is useful in doubles - can go for a dtilt and then dsmash to get the other player who's normally a bit out of range (very narrow but this could happen, and if it does, every little bit helps in 2v1s).