David Ketchum, a character actor and prolific television writer known for squeezing himself into vending machines, mailboxes and trash bins as part of his missions as a luckless secret agent on the 1960s sitcom Get Smart, died on Aug. 10 at a hospice in Thousand Oaks, Calif. He was 97. Ketchum's connection to confined spaces continued in The Elevator, a 1974 television thriller he co-wrote about a group of people stuck in an elevator.