The Trap Door Spiders met one Friday every month. Real life members, some of which are famous in their own right, were the basis for the Black Widower members:

Geoffrey Avalon...L. Sprague de Camp
Emmanuel Rubin...Lester del Rey
James Drake...Doc Clark
Thomas Trumball...Gilbert Cant
Mario Gonzalo...Lin Carter
Roger Halsted...Don Bensen

Henry the waiter is based on the famous P.G. Wodehouse character Jeeves.