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 new gags:
Remember when Kirk accidentally sat on a tribble that was in the captain's chair? This time, there is a Running Gag where a large tribble chooses the same spot. Twice, Kirk has to shove it off. The third time, 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 treatment to the tribbles which keeps them from endlessly reproducing or forming giant colony balls. Kirk notices one that's up a Jeffries tube and calls attention to it, but he has barely finished speaking when the ball disintegrates into individual tribbles and buries the captain once again.
Kirk: Some day I'll learn.
When they were on the planet where thoughts come true and someone thinks it's like "cat and mouse", a giant cat attacks them.
When the crew start de-aging in an Alternate Universe where time goes backwards, Kirk and Sulu become teens and Uhura becomes an eight-year-old. Kirk has forgotten the meanings of some sci-fi words and Uhura is crying.
Kirk explaining to a nebula-ish creature that ate them to, with lack of a better phrase spit them out. It's funny because, well, imagine hearing someone say that to you.
Kirk: "We're inside you. You thought we were food."
When Kirk and Spock turn into aquatic animals and McCoy tells them he doesn't know how to turn them back.
Kirk: "I can't give orders from an aquarium in Sickbay."