Making it so all players can see changes to a player's character(FE)?

FilteringEnabled can be tricky, but you can't change anything in a LocalScript without it being local. You need to use a server script, RemoteEvents, and FireServer.

Put this in a server script in ServerScriptService:

local Event = Instance.new("RemoteEvent")
Event.Name = "ChangeShirt"
Event.Parent = game.ReplicatedStorage

local Event2 = Instance.new("RemoteEvent")
Event2.Name = "ChangePants"
Event2.Parent = game.ReplicatedStorage

local Event3 = Instance.new("RemoteEvent")
Event3.Name = "ChangeBodyColors"
Event3.Parent = game.ReplicatedStorage

Event.OnServerEvent:connect(function(plr, id, shirt)
    if shirt ~= nil then
        shirt.ShirtTemplate = id
    else
        shirt = Instance.new("Shirt", plr.Character)
        shirt.ShirtTemplate = id
    end

    for i,v in pairs(plr.Character:GetChildren()) do
        if v.ClassName == "Accessory" then
            v:Destroy()
        end
    end

    for i,v in pairs(plr.Character:GetChildren()) do
            if v.ClassName == "Hat" then
                    v:Destroy()
            end
    end
end)

Event2.OnServerEvent:connect(function(plr, id, pants)
    if pants ~= nil then
        pants.PantsTemplate = id
    else
        pants = Instance.new("Pants", plr.Character)
        pants.PantsTemplate = id
    end
end)

Event3.OnServerEvent:connect(function(plr)
    plr.Character.Head.face.Texture = "rbxassetid://144763383"
    if plr.Character:FindFirstChild("Body Colors") ~= nil then
        local BodyColors = plr.Character:FindFirstChild("Body Colors")
            BodyColors.RightArmColor = BrickColor.new("Reddish brown")
            BodyColors.LeftArmColor = BrickColor.new("Reddish brown")
            BodyColors.LeftLegColor = BrickColor.new("Reddish brown")
            BodyColors.RightLegColor = BrickColor.new("Reddish brown")
            BodyColors.TorsoColor = BrickColor.new("Reddish brown")
            BodyColors.HeadColor = BrickColor.new("Reddish brown")
    end
        local c = plr.Character:FindFirstChild("TheFlash")
        if c then
            c:Destroy()
        end
    plr.Character.Zoom:Destroy()
    plr.Character.ReverseFlash:Destroy()
        plr.Character.BlackFlash:Destroy()
end)

Now this should be your LocalScript:

local player = game.Players.LocalPlayer
local Character = player.Character
if not Character or not Character.Parent then
    Character = player.CharacterAdded:wait()
end

local ChangeShirt = game.ReplicatedStorage:WaitForChild("ChangeShirt")
local ChangePants = game.ReplicatedStorage:WaitForChild("ChangePants")
local ChangeColors = game.ReplicatedStorage:WaitForChild("ChangeBodyColors")

script.Parent.MouseButton1Down:connect(function()
    local Head = Character.Head
    local BodyColors = Character:FindFirstChild("Body Colors")
    local Shirt = Character:FindFirstChild("Shirt")
    local Pants = Character:FindFirstChild("Pants")
    if Shirt then
        ChangeShirt:FireServer("rbxassetid://629730174",Shirt)
    else
        ChangeShirt:FireServer("rbxassetid://629730174")
    end
    if Pants then
        ChangePants:FireServer("rbxassetid://629736312",Pants)
    else
        ChangePants:FireServer("rbxassetid://629736312")
    end
    --local hat = game.ReplicatedStorage.NerdHair:Clone()
    --hat.Parent = Character
    local ReplicatedStorage = game:GetService("ReplicatedStorage")
    local WallyHat = ReplicatedStorage.Remote.WallyHat
    WallyHat:FireServer()
    ChangeColors:FireServer()
    local t = game:GetService('UserInputService').TouchEnabled
    if t == true then
    player.PlayerGui.Teleport.Minus.Visible = true
    player.PlayerGui.Teleport.Plus.Visible = true
    player.PlayerGui.Teleport.Walkspeed.Visible = true
else
    player.PlayerGui.ControlHUD.Frame.Visible = true
    script.Parent.Parent.Parent.Parent:Destroy()
end
end)

This should all (in theory) work as you want, if anything goes wrong feel free to comment and I'll try to respond as quick as possible.