The Patty Duke Show

The Patty Duke Show was an 1963-66 Dom Com starring Patty Duke as identical-looking cousins Patricia "Patty" Lane and Catherine "Cathy" Lane - one American and one Scottish. Possibly set the record for length of time between Cancellation and Reunion Show - 1999's The Patty Duke Show: Still Rockin' in Brooklyn Heights.

Currently being rerun on This TV.

American Newspapers: Martin Lane's place of employment.
Different As Night and Day: Cathy and Patty. Trope Namer by way of the Theme Song.
The Ditz: Patty's long-suffering boyfriend Richard drifts pretty near to this. It's no wonder she always seems to be on the lookout for a better option.
Double Standard: As the series goes on, Patty really shows no loyalty to Richard at all, but he always comes back to her when she'll have him.
Double Vision: Here's to you, Rita McLaughlin, whose back and shoulder went uncredited for decades...
Expository Theme Song
Mirror Routine: Done by Patty and Cathy in the first episode. The scene was then used in the opening credits.
Not Allowed to Grow Up: Paul O'Keefe as Patty's little brother Ross experiences a quite visible growth spurt toward the end of the series, but the character is still written the same way.
Sidney Sheldon: Co-creator
Standard Fifties Father: Martin Lane was hardly infallible, but he was a very understanding dad, and generally one of the most likable examples of the trope.
Twin Switch: Patty and Cathy and vice versa
Uncanny Family Resemblance: Trope Codifier
Wunza Plot: To the show's credit, while it unquestionably fits this trope, it surverts it in that really only a small percentage of episodes deal directly with Patty and Cathy's resemblance. In practice, the gimmick is mostly just an excuse for Patty Duke to play two distinct roles--which she does skillfully.
Zany Scheme: Patty comes up with them frequently.