Audiences are “bammed” by Maria Bamford, not with a clever joke or some raw assessment of American society, but by machine gunlike mimicry of several different characters — in 0 to 30 seconds.While her monologues often begin in a deceptively soft, mousy voice, she quickly shifts personas, covering a gamut of characters; a British National Geographic explorer is followed promptly by a sexual-harassing boss. Bamford has always done imitations, starting when she was young with the voices she heard on TV and her parents. A main vein for Bamford’s material is her experiences as an office temp, a familiar field for those looking to pay the bills while seeking their showbiz break. In one of her bits, Bamford relates a phone call from an overly excited temp agent: “Hello, Maria, this is T&R staffing! Here it is — the best offer! Thailand. You are sold into prostitution! $6.50 an hour and that’s not all; there’s free parking!” While temping is a means and not an end, Bamford has been able to fill in the gaps with work that requires more substance than typing 60 words a minute, including a writing stint on “The Martin Short Show” and a featured turn as a giggly waitress in the upcoming Nora Ephron laugher “Numbers,” with John Travolta and Lisa Kudrow. While many comedians will co-write on sitcoms; Bamford prefers to write for her own performances. And that is what she finds to be the absolute high of standup: casting herself in the best parts — the ones she creates.