Can I use humor in an investor presentation? (Well, the question applies to all serious presentations). I would be careful. Humor is a great ice breaker when it comes naturally, even in serious presentations such as a pitch to investors. However, making it come naturally is hard to plan. That rehearsal in front of your friends in the living room sofa is a different environment from the corporate conference room.
If you used a joke spontaneously in a previous presentation, you could try to use it again (i.e., program it), in another one if you feel that mood and energy in the room is right. But only then. And never put jokes in writing on slides or in images, you lose the option to pull them out at the last minute. Also, you do not control the digital after-life of the presentation file after the live presentation.