How do you follow a player in different games in the same universe?

I want to make a GUI that lets players follow other players. All that they would have to do is enter the username of the character. An example of what I want to do is "Apocalypse Rising".

Is the other player in the same server as the player trying to follow them? If so, this should help:

function getPlayerFromUsername(username)
	return game.Players:findFirstChild(username).userId
end

local UnlimitusId = getPlayerFromUsername(Unlimitus) --Will return 43542624, my Id.

Hope this helped.

To add to unlimitus you can use a Local Script and put game.Player.LocalPlayer instead of the Players Username