Off the cuff
Definition 1 of 2
Pro Tip 1/3Social Informality
Best used in casual conversations rather than formal situations. 
He gave an off the cuff answer to the interview question.
Pro Tip 2/3Humor Element
Often used to describe remarks that are witty or amusing. 
His off the cuff jokes always lightened the mood.
Pro Tip 3/3Unexpected Insight
Can suggest a surprising level of honesty or insight. 
Her off the cuff observations were refreshingly honest.