"They smiled at each other. All was right with the world again.
'Anyway,' the Doctor continued, 'you know what? I think you bring me luck. My Fortuna, that's you.'
'You mean I'm a sort of mascot,' said Rose. 'Like a four-leaf clover. Or wearing lucky pants when you go for an interview.'
'That's it exactly,' the Doctor told her. 'You're my lucky pants.'