The 'Teenage Dream' singer – who met the British funnyman when she was recording a cameo for his movie 'Get Him To The Greek' – says she feels she has found a "life partner" in her fiancé, and knew as soon as they met that they would be together forever.
She told USA Today newspaper: "You know when you know, and I just knew. He stopped my world. I'm wildly attracted to him. I do feel a little bit like Elvis Presley's wife Priscilla. It's been so lovely.
"He's someone I can count on, a life partner. Our relationship is a complete ongoing episode of 'I Love Lucy'. "
Although they are blissfully happy together, it was claimed earlier this week that Katy, 25, and Russell, 35, set aside an hour each day to talk with a relationship advisor in order to keep their relationship on track.
A source said: "Relationship counselling was Katy's idea because she was adamant they should make their relationship rock solid.
"As a result they both clear an hour in their schedules every day to have a conference call with a therapist, talking things over and making their bond as watertight as possible."