Spock: Captain. I am only a Vulcan. There are limits.
"More Tribbles, More Troubles" is a Call Back to TOS's most hilarious episode, "The Trouble with Tribbles" and introduces a number of throw backs and new gags:
Remember the time in TOS when Kirk sat on a tribble? This time, there is a Running Gag where a large tribble sits in that chair. Two times, Kirk has to shove it off. The third time, though, it's too large to deal with, and he concedes: "I think I'll stand."
The glommer, a critter that eats tribbles, meets a gigantic one and flees in terror.
Finally, at the end McCoy has begun to administer a cure to the tribbles which causes them not to reproduce endlessly or gather into colony balls. Kirk notices one up a chute and calls attention to it, but he has barely finished speaking when the ball disintegrates into individual tribbles and buries the captain once again. His reaction makes it funnier: