California Charlie (John Anderson)
The chipper used car dealer is all hearty enthusiasm, which of course only freaks Marion out more. His sunny, above-board extroversion contrasts sharply with Norman's shy creepiness.
Caroline (Pat Hitchcock)
Marion's coworker Caroline isn't an especially interesting character. But she is played by Alfred Hitchcock's daughter, who appeared in small roles in many of his films. Pat was a regular bit player in the Alfred Hitchcock Presents television series as well, so it's natural for her to show up here, since Psycho used much of the same crew. (See Production Studio.)
Tom Cassidy (Frank Albertson)
Cassidy is the dude with the money. He's the rich guy who leans over Marion's desk and waves $40,000 at her—and of course he's the sucker whose $40,000 Marion drives off with.
Caroline, Marion's coworker at the real estate office, notes that Cassidy was "flirting" with Marion. Cassidy, like Norman, finds Marion desirable. And, like Norman, his desire immediately precedes crime, guilt, and disaster. Sexy women in Hitchcock seem to always cause bad things… just by being sexy.
And this is why people say Hitchcock didn't like women much. (Source)
Sheriff Al Chambers and Mrs. Chambers (John McIntire and Lurene Tuttle)
A plain-speaking, small-town, upright, and god-fearing couple. You even see Mr. and Mrs. Chambers coming out of church in one of their few scenes. Al is the sheriff, of course, and he and his wife are the movie's stable island of law and normality. They're there to show you how messed up everyone else is.
Highway Patrol Officer (Mort Mills)
This is the policeman with mirrored sunglasses who is suspicious of Marion Crane when he finds her sleeping in her car by the side of the highway. The policeman isn't suspicious enough though.
The officer is an intimidating symbol of the law, but he's ultimately ineffectual. This is a film where the creepy crawly nightmares hold sway; the cops don't get to save the day.
George Lowery (Vaughn Taylor)
Marion's nervous-looking boss. He's thin and pale and jittery in a way that somewhat suggests an older Norman Bates. Marion betrays him—and then Norman kills her.