SANTA ANA, Calif. (AP) _ FBI agent Frank Calley has seen bank robbers caught because their getaway cars ran out of gas, because they robbed the branch where they did business and because the wrote stickup notes on the back of their own phone bills.

''Our clients aren't exactly Phi Beta Kappas,'' said the agent who has spent 23 years investigating bank robberies.

His favorite tale of a would-be bank job is the one about an armed robber who was knocked unconscious by a woman who got angry when he cut in front of her in line.

Similar stories abound in Southern California, the bank robbery capital of the United States with 25 percent of the nation's unauthorized withdrawals.

In one recent robbery, the robbers tried to throw off pursuers by flinging handfuls of cash out the windows of their getaway car as they drove down the freeway. The men were caught when their car spun out of control.

Then there was the ''Skateboard Bandit,'' a tanned, blond teen-ager in Bermuda shorts who fled a Newport Beach bank in apparent embarrassment when he dropped his skateboard with a clatter. He finally got up the nerve to come back and hand a teller a note demanding $100,000 cash, then changed his mind, said, ''Just a joke,'' and fled again.

When he was caught, he claimed he had been forced into the crime by a man with a bomb, Calley said.

Agents seem to delight in devising nicknames for prolific robbers: ''The Yankee Bandit,'' who nearly always wore a New York Yankees' baseball cap; ''The Great White Whale,'' said to weigh 400 pounds; ''The Twerp,'' because, Calley insisted, ''He's a twerp.''

The newest nickname in the area is for a duo dubbed ''The Marx Brothers,'' who are smarter than the average robber and have an impressive list of criminal successes to their credit. The middle-aged men often disguise themselves in curly wigs and Groucho-style mustaches before taking over a bank branch at gunpoint and cleaning out the cash drawers or vault.