An expression used for telling someone to shut up when they've been talking for way too long about something nobody cares about, especially when the subject matter is an obscure/poor quality piece of media or pseudocelebrity.
The quote itself originates from the youtube channel "Funhaus", when Bruce Greene interrupts the others as they're having a conversation about the movie "Lawnmower Man".
Lawrence: "The Lawnmower Man director, you could tell he was really building up to it cause he teased-"
Bruce: "Stop talking about. Lawnmower. Man."
(At a party)
Guy 1: If you're gonna watch Waterworld, you'd better watch the Ulysses Cut or else you'll be missing out on a lot of scenes that help explain more about the world. It also helps you get a deeper understanding of the Smokers' religious beliefs and their ability to refine-
Guy 2: Hey man, you better stop talking about lawnmower man, you're scaring the hoes away.
Fogey/fogy /fougi/ sl. (early 18C+, orig. Scot) old-fashioned, stuck-in-the mud.
Person with old fashioned ideas which he is unwilling to change: Come to the disco and stop being such an old fogey!
You think me an old fogeyand an old tory, his thoughtful voice said. I saw three generations since O’Connel’s time. I remember the famine. Do you know that the orange lodges agitated for repeal of the union twenty years before O’Connel did or before the prelates of your communion denounced him as a demagogue? You fenians forget some things. (James Joyce, Ulysses. PenguinBooks,1992. p. 38)