Acclaimed theater actor Mark Ruffalo struggled with a series of big screen flops before becoming a valuable player in the independent film world. The compact, darkly handsome player with penetrating eyes and pouty lips made his stage debut in 1990, with a role in David Steen's "Avenue A" at Los Angeles' Cast Theater. Three years later, his work in the Festival of One Acts production of Kenneth Lonergan's "Betrayal by Everyone" earned the actor notice and critical acclaim. Ruffalo reunited with Lonergan in 1996, appearing in a New Group production of "This Is Our Youth", starring as Warren