User blog comment:Nan the cowdog/TRAILER !!!!!!!!!!!!!!! :D/@comment-2133790-20110102032225/@comment-3039505-20110102034321

Oh, well on the info I found (this is already public on the Canon) it says that Phineas and Ferb accidently help Doof build a inator that will finally enable him to take over. He must have had them working for him in those overalls.