Using a joke or an amusing quote in a presentation can be a great way to win over your audience. However, there's a sure-fire way to ruin your attempts at comedy: putting the text of the joke on a slide and displaying it before you've actually said it.
Clown picture from Shutterstock
This happened repeatedly in a presentation I attended recently. The presenter had carefully hunted down a stack of relevant quotes, many of which included a punchline. But because they all appeared on screen well before he ever said them, we'd all read them in advance. Any impact from actually speaking these words was lost.
This is a specific case for one of the most basic rules of presenting: don't just read what's on your slides. Ideally, don't put the quote up on screen at all: use a relevant picture instead and save the comment itself as a surprise. If you do want to display your selectively-pilfered shard of wit, don't bring it up on screen until after you've said it -- and don't provide handouts either.