SELECT "Written by" FROM table_30383 WHERE "#" = '18'
Who wrote episode number 18?
CREATE TABLE table_30383 (
    "\u2116" real,
    "#" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" text,
    "U.S. viewers (millions)" text
)