How do you deal with this situation?

I was wondering what are some good comebacks / solutions to one of the most common situations we all face during our day to day performances. That moment when we're trying to control a card and the spectator goes "Can i shuffle the cards?".

Aside from all the technical solutions to this problem, (for example, p**m*ng the card off comes to mind), how would you diffuse the situation?

One of my solutions would be a joke "Oh, that's so nice of you to offer to help, but that won't be necessary. Thank you. I'd however need some help moving some furniture next week. are you free?" This gets a laugh and i could use that time to probably apply some sleight of hand.

Would love to hear more ideas.