Isla Fisher will never star in a movie with fiancé Sacha Baron Cohen, because working together "is the kiss of death".The 31-year-old Australian actress - who is expecting her first child with the 'Borat...' actor in October - has no plans to follow in the footsteps of previous couples such as Nicole Kidman and Tom Cruise, or Ben Affleck and Jennifer Lopez and share a screen with her partner, because it always ends in disaster. She told Britain's The Times newspaper: "God, no! I mean, how successful are married working relationships? Nicole and Tom split up after 'Eyes Wide Shut'. Sandra Oh and her director husband Alexander Payne separated after 'Sideways'. I feel like working together is the kiss of death."The diminutive 'Wedding Crashers' star also revealed she feels like a "circus freak" next to her towering lover.She added: "I really enjoyed not being noticed, but we're starting to have our pictures taken a little more often now. I think it's because Sacha's so tall while I'm so small. I'm like a circus freak!"Isla - who will next star in the comedy 'Hot Rod' about a stuntman who plans to jump 15 buses on a motorcycle - added she was happy to convert to Judaism so she could marry Jewish Sacha.The actress, who has been dating the comic star for five years, revealed: "We're definitely going to have a beautiful traditional Jewish wedding. I'd do anything to ensure our future together as man and wife. To that end I've been learning about Judaism, which I find very beautiful. It has enriched my life enormously. I love religions and find them fascinating."