Bonanza - Season 1 - Eps 21: The Spanish Grant
In "The Spanish Grant", a young bargirl, Rosita Morales is pretending to be a Spanish noblewoman named Isabella Marie Inez de la Cuesta and at the end of the story, it's revealed she is really Rosita Morales, but on the other hand, is she really Rosita Morales? This little twist at the end is simply entertaining everytime it's viewed, with the viewer able to determine the young woman's real identity at the end of act four.
About Bonanza

Title: Bonanza
First Air Date: 1959-09-12
Last Air Date: 1973-01-16
Status: Ended
Rating: 7.5/10 (from 440 votes)
Language: EN
Seasons: 14
Total Episodes: 431
Network: NBC
Genres: Western, Action & Adventure, Drama, Family
Production Companies: NBC, NBC Studios
Synopsis
The High-Sierra adventures of Ben Cartwright and his sons as they run and defend their ranch while helping the surrounding community.
Cast

Lorne Greene
Ben Cartwright

Michael Landon
Joe Cartwright

David Canary
Candy Canaday

Tim Matheson
Griff King

Mitch Vogel
Jamie Hunter Cartwright