Although I prefer the humour in the original phrasing, the following phrasing would conform more to the other items on this list. Will it do?

69. Clark may confuse those little black box things with wires sticking out of them with fresh veggies. If so, remind him that they are explosive devices and he doesn't have to swallow them. Also remind him that it is not a good idea to sit on one - an explosive device or fresh veggies.

Joy,
Lynn

edit: I see Virginia beat me to the punch, and her version is closer to the original than mine. (Although I must admit that when I first read the rule, I heard Martha's voice, rather than Lois', giving that advice.)