This could be your big break. On Friday the 13th, the Northwest Film Forum delivers its 24-Hour Film Challenge. Show up at 8 p.m., learn your mission (”think of Lars von Trier’s challenges to Jergen Leth in The Five Obstructions,” they say) and come back the next evening with a masterpiece based on this year’s theme, Curiosities. Entries will be screened on Halloween, so make it scary!