The series starred Don Adams as bumbling secret agent Maxwell Smart, Agent 86. Barbara Feldon's character had no name; even after Smart married her, he (and everyone else) would always address her as "99." Smart and 99 worked for Control, a secret U.S. Government spy agency. The nemesis of Control was KAOS, headed by a mysterious eastern-European spymaster named Sigfried (Bernie Kopell). Other characters included the Chief of Control, whose first name was once revealed as Thaddeus but who was always addressed as Chief (Ed Platt); Agent 44, who was always disguised as a planter, mailbox, or other object; and Agent Larrabee (Robert Karvelas), the Chief's assistant.
Many taglines and schticks have endured:
"Sorry about that, Chief." "Would you believe..." "Missed me by that much." "Don't tell me .... I told you not to tell me that." "Max!"
Smart would communicate with Control using a dial telephone concealed in his shoe (a "shoe phone").
Smart would always insist on following the rules and, when in the Chief's office, would insist on speaking under the Cone of Silence (two plastic hemispheres which were electrically lowered on top of Smart and the Chief, and which invariably malfunctioned).