It's a Mad etc was a frenetic treasure hunt that had a cast of thousands, and was written by Bill and Tania Rose.  That's the Tania Rose who still lives in the downstairs apartment from me.

This potted history downplays Tania's role somewhat (and her tolerance !) but is worth a read: http://en.wikipedia.org/wiki/William_Rose_%28screenwriter%29 .

This little Czech poster for the film's first release there in 1966 (rest of the world '63-'64) is quite charming compared to the over the top artwork on most posters for this blockbuster. Leading cast members shown are Spencer Tracy, Terry-Tomas, Sid Caesar, Dorothy Provine and Edie Adams. The director was Stanley Kramer.