Some advice on telling jokes on the spot

I was told the other day since I have been doing some comedic performances to tell a joke on the spot.

I am not a stand-up comedian so I do not have a whole set of jokes ready at the mark to entertain random folks or acquaintances.

I do now however have the perfect response for this question - that I can up with on the spot when asked to tell a joke...I guess the perfect response is a joke but that is not the point.

Here is my perfect response to if someone asks me for a joke:

Sorry I don't know any jokes. (that's just the opening - not the joke)
I'm just full of wit and hilarity and so my jokes are like lasers, you never know when one is coming (laser sounds).

The key is finishing with laser sounds as everyone loves the sounds of lasers.