How would I set someones ROBLOX FPS?

To create a sort of "lag" effect on someone. Any wiki articles about it can help, I'm just not sure what to look up though.

If I am correct, there is NO possible way to set someone's FPS. The only way to make someone lag is either they having a laggy and bad computer, or you just completely filling your game with nonsense and HUGE stuff, or putting in scripts that could potentially lag the server. Other than that, you can't really make a person lag from scripts (depending what the script contains or does) or you can't set people's FPS.