"It is better to be a fool than to be dead," declared Robert Louis Stevenson in Crabbed Age and Youth. The First Church of the Last Laugh agrees -- this is the 20th time they've staged April Fools' Day celebration the St. Stupid's Day Parade. Stupidity and tomfoolery are not just encouraged, they're organized in this parade, which weaves through the Financial District blessing bankers' hearts and, with a biblical flourish, visiting the stations of the stupid. A leap of faith and a sock exchange in the vicinity of the Pacific Stock Exchange are also scheduled. The parade begins around noon in Justin Herman Plaza, Market & Steuart, S.F. Admission is free; call (510) 841-1898. The levity continues at the opening of the Schmulowitz Collection of Wit and Humor, an assembly of 20th-century comic art by strippers like Gary Larson, Lynda Barry, and Nicole Hollander, plus back issues of Mad, essays by the likes of Ian Shoales and Spalding Gray, and recently bequeathed comedy records, all to be displayed under glass. The late Nat Schmulowitz, a San Francisco attorney who had his own philosophy on the mental health benefits of a good laugh, amassed thousands of books and magazines in 35 languages, but in the interest of limited space, the exhibit concentrates on American work. It opens today (and runs through May 31, with comedy films screening Thursdays in May) at the Main Library, 100 Larkin (at Market), S.F. Admission is free; call 557-4560. Lastly, the FoFest gets American theatergoers acquainted with the political satire of '97 Nobel Laureate Dario Fo and his partner, actress/playwright Franca Rame. As it turns out, San Francisco was among the first American cities to stage the Italian writer's work, beginning with the S.F. Mime Troupe's production of We Can't Pay! We Won't Pay! in 1979. Mime Troupe resident playwright and Fo translator Joan Holden and others participate in a panel discussion of Fo's work (April 19 at the Museo ItaloAmericano); the fest also includes performances of Fo's work on film (April 17 at the Italian Cultural Institute and April 19 at Museo ItaloAmericano) and "Celebrating Dario and Franca: Scenes From the Great Bay Area Fo Productions," with original actors reprising their roles in productions that poke fun at the folly of authority figures and restore dignity to the little people (April 20 in the Cowell Theater). "Celebrating" tickets go on sale today; call the Cowell Theater box office at 441-3687 to reserve seats or get more information.