Castle's one of my favorite shows currently on tv!

If I'm not mistaken at least one of the writers that used to work on Lois and Clark is currently a writer over on Castle. I also vaguely remember hearing a quote about how they are similar (and referenced it WAY more than Moonlighting.)

I'm not sure if I could imagine a crossover between the two but it might be worth a shot. The character dynamics are reminiscent of each other.

CLARK: No. I'm just worried I'm a jinx.
JONATHAN: A jinx?
CLARK: Yeah. Let's face it, ever since she's known me, Lois's been kidnapped, frozen, pushed off buildings, almost stabbed, poisoned, buried alive and who knows what else, and it's all because of me.
-"Contact" (You're not her jinx, you're her blessing.)