10:36:56.350 - ServerScriptService.Stats:41: attempt to index nil with 'Humanoid'
player.CharacterAppearanceLoaded:Connect(function()
local humanoid = character.Humanoid
humanoid:WaitForChild("BodyDepthScale").Value = .5 + (strength.Value / 250)
humanoid:WaitForChild("BodyHeightScale").Value = .5 + (strength.Value / 250)
humanoid:WaitForChild("BodyWidthScale").Value = .5 + (strength.Value / 250)
humanoid:WaitForChild("HeadScale").Value = .5 + (strength.Value / 250)
humanoid.WalkSpeed = 16 * (strength.Value / 250)
end)

2 comments
Where did you define the character var?
Maybe "character = player.Character or player.CharacterAdded"(inside the event)