Script with the purpose of putting a model on the players head problem?

I'm currently having trouble with making this script that has the purpose of putting a model on top of the players head. I tried to do it but I got the error called "Badcast" can anyone tell me what that is and where it is in my code? Also if you can point out any other major flaws in the script it would be a huge help. I am new to scripting so apologies if it is obvious.

game.Players.PlayerAdded:Connect(function(Player)
if Player:GetRankInGroup(3617016) == 255 then

end
end)
local hit = game.ServerStorage.Pickelhaube


local g = game.ServerStorage.Pickelhaube:clone()
        g.Parent = hit.Parent
        local C = g:GetChildren()
        for i=1, #C do
            if C[i].className == "Part" or "Unionoperation" then
                local W = Instance.new("Weld")
                W.Part0 = g.Middle
                W.Part1 = C[i]
                local CJ = CFrame.new(g.Middle.Position)
                local C0 = g.Middle.CFrame:inverse()*CJ
                local C1 = C[i].CFrame:inverse()*CJ
                W.C0 = C0
                W.C1 = C1
                W.Parent = g.Middle
                g.Middle.Transparency = 1
            end
                local Y = Instance.new("Weld")
                Y.Part0 = hit.Parent.Head
                Y.Part1 = g.Middle
                Y.C0 = CFrame.new(0, 0, 0)
                Y.Parent = Y.Part0

        end

        local h = g:GetChildren()
        for i = 1, # h do
            h[i].Anchored = false
            h[i].CanCollide = false


end