user: Question: Who was Marcus's guest in the episode when Rufus's guest was Rory McGrath?
Columns: ['Episode', 'First broadcast', 'Rufus guest', 'Marcus guest', 'Winner']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['2x01', '23 March 2009', 'Chris Addison', 'Dara Ó Briain', 'Red (3–2)']
SQL:

assistant: SELECT "Marcus guest" FROM "Table" WHERE "Rufus guest" = 'Rory McGrath';