This classic moment of Nick taking a call from a man whose car was stolen.
"Mr. Revelli? Will you hold a minute? I gotta find a pencil. [uses the pencil as a replacement chopstick for his lunch] Okay go ahead."
And then after he's hung up: "Oh my god, I ate my eraser."
The brownies episode. Unbeknownst to Wojo, the brownies his girlfriend has baked are laced with hashish, and he shares them with Fish, Harris, and Yemana. By the middle of the episode, all four are stoned out of their gourds - Yemana keeps breaking into song, Harris is grinning like a loon, and Fish jumps across rooftops to collar a suspect a third of his age and actually stands up to defend Bernice's honour. The next day, Barney, the only one not to sample the brownies, suggests the other detectives forget the whole incident. Luckily for him, they don't need to pretend - they actually have forgotten it.
In one episode, an Air Force general visits to report calls he received from someone threatening to blow up his base. It is implied that he fought as a pilot in World War II, and can barely contain his prejudice when he sees Lt. Yemana, a Japanese-American cop. Yemana has fun needling him over it;
General: It just isn't right. Why would someone threaten to blow up a U.S. military installation?
This exchange in "The Counterfeiter," after the man who turned in the money learns that he's out $35 for being honest and not fobbing it off on someone else.