When the Enterprise stops at the K-7 space station to pick up a shipment of a new type of grain, trader Cyrano Jones introduces the Enterprise crew to tribbles, cute furry creatures that multiply so rapidly that they almost fill the Enterprise to its seam
Air Date: 12/29/67
Director: Joseph Pevney
Here we have one of the top 5 TOS episodes and easily one of the top Star Trek episodes ever made. It's funny as heck and probably one of the most accessible episodes of the original series - making it a great episode to show anyone you want to introduce to Trek.