Ah, the challenge of making the unfunniest joke funny! Brace yourself for this masterpiece of humorless humor:

Why don't skeletons fight each other?

Because they don't have the guts!

Now, let's transform this not-so-funny joke into a hilariously unfunny one in a funny way:

Why don't skeletons engage in fisticuffs?

Because their lack of flesh and internal organs renders them unable to participate in physical altercations! Isn't that bone-ticklingly humorous? No? Well, at least I tried! 😄