Is it frowned upon to add slight humor and sarcasm to academic presentations? For example, I flip to a background slide and say "This is a typical slide used by researchers in (field) just to show off how difficult their work is." before going through the content of the slide. Is there a difference in doing that in different settings, like a department seminar vs an international conference?
There is nothing wrong with a little humor as long as you can pull it off well. Lightening the mood is often welcome, especially in settings where the expected norm may be long, dry boring, content (such as a conference where people are attending session after session all day).
Besides making people laugh, a joke or two in an academic presentation can help make you and the audience more comfortable, make your presentation more memorable, and help you come across as a confident, competent presenter.
Of course, there are potential downfalls:
- A joke could fall flat, which may be awkward and embarrassing.
- Jokes that might come across as insulting can be dangerous (though gently poking fun at your own discipline can be fine--I have no problem with your proposed statement, especially if you make it self-deprecating, such as "I have made this slide extra complicated so I seem important". I have taken this approach and it usually goes down very well.)
- Too much humor can distract from your message. Use a little humor, and it helps engage people, and they will be paying attention to your serious point. Use too much, and no one will remember anything but the jokes.
But overall, I say go for it. Having a boring, forgettable presentation is a much bigger danger than a joke that falls flat.
I'd say you should know what audience you're presenting to. If you're presenting groundbreaking (or at the very least, important) information at an international conference full of notable researchers in the field, you might be able to get away with a single joke or sarcastic comment. Most people are there to learn, not to laugh.
On the other hand, if it's among people who know you well (e.g. department seminar or something of the like), you can add a little more humor to lighten the mood a bit.
One thing to take away from my answer is that you should reread your question: you're giving an academic presentation, not touring as a stand-up comic. A little humor can be well-received, but too much will make you seem foolish.
One thing to consider is that humour is subjective. Not everyone finds the same thing funny, and it's possible that not everyone will realise that a statement is a joke. As a comment on another answer points out, this is particularly true if the first language of the audience isn't the same as that of the speaker.
In particular, unless you know your audience very well, don't make hyperbolic statements on the assumption that your audience will realise they are untrue. 95% of the audience might find "and this identity can be used to solve five other grand challenge problems before breakfast" mildly amusing, but the PhD student who wastes a month following up on idea won't.