Why does't the value change?

local mouse = game.Players.LocalPlayer:GetMouse()
local p = workspace.part
local plr = "Head"

while true do
    wait()
    if mouse.Target == nil or mouse.Target == p  then
        script.Parent.Value = ""
    elseif mouse.Target == plr then
        script.Parent.Value = plr.Parent.Name
    else
        script.Parent.Value = mouse.Target.Name
    end
end

Everything works except elseif mouse.Target == plr then script.Parent.Value = plr.Parent.Name

Whenever I mouse over a head the value is 'Head' and not 'Player1' (the head belongs to 'Player1')

No errors either.