What does attempt to index upvalue 'Character' (a nil value) mean?

local Player=game.Players.LocalPlayer
local Character=Player.Character
local Mouse=Player:GetMouse()

Mouse.KeyDown:connect(function(K)
    if K=="q" then
        local Frog=workspace.Frog:Clone()
        Frog.Parent=workspace
        Frog.CFrame=Character.Torso.CFrame+Vector3.new(0,5,0)
        while Mouse.KeyDown:connect(function(Q)end)do
            wait(1)
            if Q=="q" then
                Frog.Size=Frog.Size+Vector3.new(.1,.1,.1)
            end
        end

            Mouse.Button1Down:connect(function()
        Frog.Anchored=false
        Frog.BodyPosition.position=Mouse.Hit.p
        local Debris=game:GetService("Debris")
        wait(5)
        Frog.BrickColor=BrickColor.new("Really black")
        Debris:AddItem(Frog,5)
        end)
    end
end)

This works fine until I start a server, and the output says

attempt to index upvalue 'Character' (a nil value)

what am I doing wrong? thank you in advanced