CREATE TABLE table_19930660_2 (marcus_guest VARCHAR, rufus_guest VARCHAR)

Who was Marcus's guest in the episode when Rufus's guest was Rory McGrath?
SELECT marcus_guest FROM table_19930660_2 WHERE rufus_guest = "Rory McGrath"
SELECT "marcus_guest" FROM "table_19930660_2" WHERE "Rory McGrath" = "rufus_guest"