Bartender4 

function IconIntroTracker_OnEvent(self, event, spellID)
  if event == "SPELL_PUSHED_TO_ACTIONBAR" then
    local _, _, icon = GetSpellInfo(spellID)
    local freeIcon, frame

    for slot = 1, 120 do
      local btn, otype, oID = _G["BT4Button"..slot], GetActionInfo(slot)
      if btn and btn:IsShown() and otype == "spell" and oID == spellID then
        frame = btn
        break
      end
    end

    if not frame then
      return -- no frame with the spell found, no animation will be shown
    end

    for key, obj in pairs(self.iconList) do
      if obj.isFree then
        freeIcon = obj
      end
    end

    if not freeIcon then
      freeIcon = CreateFrame("Frame", self:GetName().."Icon"..(#self.iconList+1), UIParent, "IconIntroTemplate")
      self.iconList[#self.iconList+1] = freeIcon
    end

    freeIcon.icon.icon:SetTexture(icon)
    freeIcon.icon.slot = frame.id

    freeIcon:ClearAllPoints()
    freeIcon:SetPoint("CENTER", frame, 0, 0)
    freeIcon:SetFrameLevel(frame:GetFrameLevel()+1)

    freeIcon.icon.flyin:Play(1)
    freeIcon.isFree = false
  end
end