The Dink Network

Well, there was once in Dink's house by the savebot with Nadine's Ultimate attack cast directly onto David, another at the first spider encounter using multishot, and it's happened with the normal shot (though I think it was pierce on that instance). I don't think the location would have anything to do with it.

I've had the most success replicating this at Dink's house using multishot with little to no charge, but it happens quite often in battle.