Second City, an institution since 1959, has served as a launching pad for some of the hottest comedians around. Alumni include Dan Aykroyd, Tina Fey, Amy Poehler, and the late John Belushi. It's the anchor of Chicago improv. The revues on the company's main stage and in its smaller e.t.c. space next door are actually sketch comedy shows, but the scripts in these pre-rehearsed scenes have been developed through improvisation and there's usually a little time set aside in each show for the performers to demonstrate their quick wit. Most nights there is a free improv set after the late show, featuring cast members and invited guests (sometimes famous, sometimes not, never announced in advance). It's in Donny's Skybox upstairs that you're more likely to see one of Chicago's many fledgling improv comedy troupes making their first appearance working together on freshly penned material in public.