My sister has been happily married for 25 years to a guy with one of the quickest wits I have ever met. Here is just a sample:
He, a buddy of his and my sister are walking down the street one day when they spot a dog lying in the sun licking himself in the usual places. The buddy spots the dog and for no apparent reason blurts out "man, I wish I could do that!" My BIL rejoions equally quickly "go ahead, he won't mind."
Ever had a flash of inspiration afterwards where you wished you had said it back then? One from my long gone Mother -
"Turn back, turn back, time in thy flight! I thought of the line I needed last night ..."
- Apologies to Mr. Shakespeare