This is probably the most lightweight episode ever although there are also some serious issues as well. The reason for the enterprise's being where it is, is that they need to get some seed grain to another planet. William Schallert who played intellectual types throughout his career, is the pesky overseer in this one. He is constantly on Kirk's case because he is unhappy with his lack of seriousness. Meanwhile, on the planet, a man named Cyrano Jones, a traveling merchant, peddling junk, begins to distribute a little purring animal called a Tribble. They make people feel happy at their touch. They are soft and pretty. They are also perpetually pregnant and soon every nook and cranny is filled with Tribbles. The other side of the issue is that they are voracious eaters. It isn't long before the storage bins are compromised and the grain in the bins is replaced with Tribbles. There are some great scenes between the Enterprise crew and the Klingons, who have been sharing space with Kirk's crew. There is justice eventually, but not before a series of delightful events.