Add a accessory to a player?

I usually just make the accessory's parent into StarterCharacterScripts

Humanoid documentation includes a function "AddAccessory" to do just that!

An example would be this:

if workspace:FindFirstChild("Pumpkin") then
    game.Players.PlayerAdded:Connect(function(player)
    -- Check if the character exists to prevent a crash
    if player.Character then
        local accessory = workspace.Pumpkin -- :Clone()
            player.Character:WaitForChild("Humanoid"):AddAccessory(accessory)
    end
    end) 
end

or optionally you could do this:

if workspace:FindFirstChild("Pumpkin") then
    game.Players.PlayerAdded:Connect(function(player)
    -- Error handling
    local result,err = pcall(function()
        local accessory = workspace.Pumpkin -- :Clone()
            player.Character:WaitForChild("Humanoid"):AddAccessory(accessory)
    end)
    if not result then
        warn(err) -- Display any errors without breaking the code
    end
    end) 
end

You can put the Pumpkin into ServerStorage:

game.Players.PlayerAdded:Connect(function(player)
player.Character.Humanoid:AddAccessory(game.ServerStorage.Pumpkin:Clone())
end)

Bad formatting on mobile