While Karl throws himself into finalising Susans surprise party, hes unaware Susan is completely aware of the ruse, but is more than happy to go along with it, relieved she is now his number one priority. When the suggestion of Izzys unwelcome attendance is raised, Susan pre-empts any trouble by inviting Izzy herself. Karl is overjoyed with Susans reaction to the party, but when Izzy arriv... (thetvdb.com)