 Why does the narrator say that the aliens' jokes are dangerous?
The most dangerous of weapons is the one you don't know is loaded. Illustrated by Schoenherr The wind howled out of the northwest, blind with snow and barbed with ice crystals. We got lined up between Earth and Mars, you'll remember, and James pushed the button marked 'Jump'. Walking, talking natives on a blue sky planet with 1.1 g gravity and a twenty per cent oxygen atmosphere at fifteen p.s.i. When I say they, I mean a ten-man team of them. People who talk English, drink beer, like jokes and beat me at chess or table-tennis are people for my money, even if they look like tigers in trousers.
 The wrong kind of joke could end in catastrophe
 The wrong kind of joke could end in catastrophe  It hurts the scientists' reputations to be beat at games like chess  Their practical jokes tend to meddle with spaceship parts  They like to play with weapons and people tend to die