Well, there are conjoined twins in real life and we can tell a story about them so long as they're not the brunt of the jokes. In this, they're the heroes of this story; we love these guys.
“It's hard to tell whether the ship or airplane - they're all the same, I'm convinced - is male or female; it may shift back and forth.”
“A total nuclear freeze is counterproductive - especially now, when technology is rapidly changing and the Soviets have some important strategic advantages.”