be in like Flynn
be in like Flynnseize an opportunity; be successful. Australian
The Flynn referred to in this expression is Errol Flynn, the Australian-born actor, who had a reputation as a notable playboy.
1987 Kathy Lette Girls' Night Out Russell brightened. ‘Really?’ I'm in, he thought to himself. I'm in like Flynn. ‘You really see it that way?’ He slid his arms around her.