Martin Starr
Wikipedia’s filmography for Martin Starr lists his screen credits in chronological order. Everything before Eyeball Eddie (2001) is either a guest spot on a television series (G vs. E, Normal, Ohio, Ed, Mysterious Ways) or a supporting ensemble role (Freaks and Geeks, as Bill Haverchuck, one of several teenage leads rather than the sole lead). Eyeball Eddie, in which he plays the title character, is the first credit in which he is the lead.