It says "Unknown Global 'player'"?

Here's the script ``local cost = 500

local petModule = require(game.ServerScriptService:WaitForChild("PetModule"))

script.Parent.ClickDetector.MouseClick:Connect(function()

if player.leaderstats.Cash.Value >= 500 then

	player.leaderstats.Cash.Value = player.leaderstats.Cash.Value - cost

	local pet = petModule.chooseRandomPet()

	print(pet.Name.." selected")

	game.ReplicatedStorage.HatchEgg:FireClient(player,pet)

end

end)

This is because you haven't defined the variable player yet. try putting

script.Parent.ClickDetector.MouseClick:Connect(function(player)