This animation won't play online

script.Parent.ClickDetector.MouseClick:connect(function(playerWhoClicked)
local animation = Instance.new("Animation")
animation.AnimationId = "http://www.roblox.com/Asset?ID=147619125" -- your id here

local animTrack =script.Parent.Parent:FindFirstChild("Humanoid"):LoadAnimation(animation) 
-- change Humanoid to the target's Humanoid

animTrack:Play()

end)

It works in test mode but not in a server

Unless you're loading in to a NPC ( not a character ) the wiki says it has to be a LocalScript.

--LocalScript in StarterGui or StarterPack

repeat wait() until game.Players.LocalPlayer

local PartName = "Part1" --Name of the part you want to click.
local animationId = "http://www.roblox.com/Asset?ID=147619125"
local p = game.Players.LocalPlayer
local mouse = p:GetMouse()

mouse.Button1Down:connect(function()
	if mouse.Target and mouse.Target.Name == PartName then
		local new = Instance.new("Animation")
		new.AnimationId = animationId
		p.Character.Humanoid:LoadAnimation(new):Play()
	end
end)

script.Parent.ClickDetector.MouseClick:connect(function(playerWhoClicked)
local animation = Instance.new("Animation")
animation.AnimationId = "http://www.roblox.com/Asset?ID=147619125" -- your id here

local animTrack =playerWhoClick.Character:FindFirstChild("Humanoid"):LoadAnimation(animation)
-- change Humanoid to the target's Humanoid

animTrack:Play()

end)

You aren't loading the animation on the script's parent, you want to find the character's humanoid so take the player value that the event returns and then find the character and it's humanoid then load the animation!