How can I change a person to another character?

If this helps. :)

--[[
	Put this script in StarterGui.
	Script by JustGimmeDaBux
	Feel free to remove ^^!
	Enjoy!
--]]

--These two, while being capable of being IDs can also function as randomized arrays of clothing
--Y'know, in case you wanna spice things up. >:3

--Take the AssetID(the random numbers at the end of the URL when looking at a shirt/pants
--and subtract it by 1 to get the IDs
local shirtIDs = {"ID","ID","MOREIDS","MOREIDS"}
local pantsIDs = {"ID","ID","MOREIDS","MOREIDS"}

--[[
	It sounds a bit mean, but the CFraming of hats is a very hat-specific process,
	and I really couldn't work in a way of making Hats modular. I'll continue to work on this one!
	Also working on body colors!
--]]


--[[
	This first function basically just cleans out the stuff the character is already
	wearing. I don't suggest messing with it as the code here is a bit... messy. :S
--]]
function CleanUpJunk(char)
	local stuff=char:GetChildren()
	for _,junk in pairs(stuff) do
		if junk.Name~="Health" and junk.Name~="Sound" and junk.Name~="Humanoid" and junk.Name~="Animate" and junk.Name~="Head" and junk.Name~="HumanoidRootPart" and junk.Name~="Left Arm" and junk.Name~="Right Arm" and junk.Name~="Left Leg" and junk.Name~="Right Leg" and junk.Name~="Torso" then
			junk:Destroy()
		end
		if junk.Name=="Torso" then
			junk.roblox:Destroy()
		end
	end
end
--[[
	Alright, the ugly mess should be out of the way now. Now we get to do the FUN stuff! :DDDD
--]]
function CreateOutfit(char)
	
	--Make le shirt
	local randomShirt=math.random(1,#shirtIDs)
	local shirt=Instance.new("Shirt")
	shirt.Parent=char
	shirt.Name="Shirt"
	shirt.ShirtTemplate=("http://www.roblox.com/asset/?id=" .. shirtIDs[randomShirt])
	
	--Make le pants
	local randomPants=math.random(1,#pantsIDs)
	local pants=Instance.new("Pants")
	pants.Parent=char
	pants.Name="Pants"
	pants.PantsTemplate=("http://www.roblox.com/asset/?id=" .. pantsIDs[randomPants])
	
	local colors=script:FindFirstChild("Body Colors")
	colors:Clone().Parent=char
end

wait(3)
local char=game.Players.LocalPlayer.Character
CleanUpJunk(char)
CreateOutfit(char)

Have fun!