What's in the box, in the box, what's in the box today?
A note is placed on top, which just has a smiley face on it, signed "BVL" in big, easily visible letters. The cautious individual may be wary of the box's contents once they realise the gift-giver, but that plays into Vivean's trap:
If opened immediately, the box is harmless, and reveals its contents to be a playful party hat that changes colours and patterns, underneath which is a bottle of Odgen's Old Firewhiskey, single malt and aged beautifully.
If the box-opening is delayed (for whatever reason. It doesn't discriminate), just before noon, it will burst open of its own accord, spilling dozens of gummy worms, all of them charmed to try to attach themselves to Benny's face, either as a mustache or as eyebrows. Each worm can be taken care of with a finite incantatem, but good luck trying to catch all of them. The worms can be eaten, and in the box is still that party hat and the firewhiskey.