Frankenstein: Hey witch, can you make me a glass of lemonade?
Witch: Poof!  You’re a glass of lemonade!

Explanation: The word ‘poof‘ in this joke is the sound of a witch casting a spell.  (I could have used the word zap or another magic word.)

When you hear the question, “Can you make me a lemonade?” you expect the answer to be a yes, a no, or something like that. Maybe a, “Sorry, we have no lemons.”  In this case the witch turned Frankenstein into a glass of lemonade with magical powers and that makes this joke funny.

Here is a summary of the book Frankenstein, by Mary Shelley: