WELLS ST, RENAISSANCE:The gang at Second City rolls merrily along, maintaining Chicago’* reputation for spawning improvisatory and off-beat cabaret, and crowding the customers into the smoke-filled room out North, “Animal Fair,** latest Second City production, includes, among its better items,a session at the Art Institute with graphic comments on abstract painting and a culminating exchange between a beatnik and a girl afraid to stray from her analyst; a killing sketch involving the revival of football at the University of Chicago as envisioned by a bewildered coach and three avant garde varsity candidates; a funny and rowdy parody of a grand opera, and so weiter, The company attains real satiric stature in a scene between a ganghng, lone-Iv city-dweller and a long-playing record offering him mechanized paiship.The company’s talents emerge: into sharper focus as the weeks pass by, and the gifts of such as Eugene Troobnick, Andrew Duncan* the dead-pan M.C.. Paul Sand, that extraordinary mime, 'and Mina Kolb, the pretty little ! comedienne, become more endearing, Special kudos should fall to Bill Mathieu who lurks upstage making music on piano and horn, backing up the whole business.