If we are talking about jokes there is one I remember from SVU:
The was a murder in a dive hotel.
Stabler(to desk clerk): Has the room been cleaned?
Desk clerk: Not since 1957.
Every once in a while there’s a minor witness who I feel sure is played by an actor who wants to be certain to be noticed for their one-minute scene, and plays the heck out of their part.
They were big on interviewing suspects on the job actively working. I think it might have been SNL that did a parody of this. The actors were often hamming it up in those scenes, and also the people who discover the dead body at the beginning and are usually not seen again on the episode. A small part on L&O is a pretty good gig for a budding actor, they oughta take advantage of it.
Kevin Smith was offered a part; they asked if he wanted to be a judge or an attorney, something like that. He said he wanted to be the guy who points them to the guy who points them to the killer.
And so he was.
“Tony’s wife’s nephew.” Didn’t even get a name.
As opposed to a character who unwittingly enters the room while the detectives are questioning someone else. Nine times out of ten, that ends up being the murderer.
No complaints about the writing, or show quality, just “one and done”. That’s OK.
If he hadn’t just died, they could use Bruce MacVittie in the detective role. Roy Thinnes is still alive, he could replace McCoy. 