Today, the Upright Citizens Brigade is a bicoastal force and national comedy brand. But in 1999, when founding members Matt Besser, Amy Poehler, Matt Walsh, and Ian Roberts opened their first theater in a former strip club, nobody would have mistaken it for a landmark. The quartet opened the shabby dive as a haven for long-form improv; there, they performed their weekly Sunday night ASSSSCAT shows (joined by Saturday Night Live cast members and Late Night with Conan O’Brien writer/performers trying to stay in fighting improv shape) and taught a new generation of comedians their craft. Looking back on this era is like seeing the origin story of today’s TV comedy casts: People like Rob Corddry, Huebel and Riggle, Aziz Ansari, Aubrey Plaza, Ed Helms…