1. "Cavender Is Coming"

The Twilight Zone, 1962

When a laugh track appears in a Twilight Zone episode, you know something funny is going on. Well, unfortunately, this comedic outlier was not very funny, despite featuring a young, up-and-coming Carol Burnett. The tale centered around a guardian angel, played by Jesse White, the actor best known as the Maytag repairman. It fizzled. Rod Serling had hoped to create a Cavender sitcom. However, as a writer, he was better suited to uncanny science fiction. These days, the episode is shown minus the laugh track, at least.

2. "The Moonglow Affair"

The Man From U.N.C.L.E., 1966

With the success of The Man From U.N.C.L.E., it just made sense to have The Girl From U.N.C.L.E., too. Indeed, Napoleon Solo's female counterpart, April Dancer, would earn her own show for one season. Stefanie Powers played Dancer on the series. However, when the character was introduced earlier in "The Moonglow Affair," she was portrayed by Mary Ann Mobley. Her original onscreen partner, played by Norman Fell, was replaced, too.

3. "Assignment: Earth"

Star Trek, 1968

Pity that Gary Seven never got the series he deserved. Robert Lansing portrayed the mysterious alien man, armed with his "servo" — a sort of high-tech pen — and a resistance to Vulcan nerve pinches. This episode served as a backdoor pilot for a series featuring both Lansing and costar Teri Garr. Seven contacts the Enterprise as he attempts to thwart a nuclear doomsday on earth, circa 1968.

4. "His Two Right Arms"

The Mary Tyler Moore Show, 1972

Mary gets City Councilman Pete Peterson to appear on 'Face the People' and discovers that he is completely incompetent. She and his aides try to bring him up to speed on current events so he can make a good impression on the show. Naturally, comedy ensues. Bill Daily played Pete Peterson and was meant to get his own show. No worries, as he scored a major role on another MTM Enterprises series, The Bob Newhart Show.

5. "Kelly's Kids"

The Brady Bunch, 1974

This season five episode of The Brady Bunch also served as a pilot for a potential spin-off of the same name. The character Ken Kelly, played by Ken Berry, lived next door to the Bradys and adopted three children of different racial backgrounds. Despite an intriguing plot, the show wasn't picked up, partially due to The Brady Bunch's low ratings during the end of its run.

6. "The Girl from Ilandia"

Wonder Woman, 1978

Wonder Woman meets a young girl, Tina, from another world who has very special powers, and convinces her to stay in this world to keep it safe from enemy agents. The results are surprisingly emotional. Oh, and Tiger, the dog from The Brady Bunch, also appeared in what would have been a charming teen fantasy series.

7. "Chachi Sells His Soul"

Happy Days, 1979

Fonzie aficionados continue to debate whether "Chachi Sells His Soul" is a backdoor pilot for Out of the Blue or merely a crossover. The spin-off actually aired days before the Happy Days episode that "introduced" the guardian angel named Random. Yep, another guardian angel concept! However, watching "Chachi Sells His Soul" — in which, indeed, Chachi strikes a Faustian deal with the devil's nephew — it certainly feels like a backdoor pilot. Out of the Blue made it to series, but only lasted a handful of episodes. Hey, not every Happy Days spin-off could be Mork & Mindy or Laverne & Shirley.

Image: jimbroganonline.com

8. "Here Today, Hair Tomorrow"

Laverne & Shirley, 1983

Speaking of Laverne & Shirley, this spin-off (of a spin-off) also tried to spawn its own spin-off! The beloved sitcom went out with an odd whimper in this final episode, that hardly features any familiar characters. Carmine (Eddie Mekka) moves to New York and tries to land a role in Hair. Alas, audiences were not interested in following Shirley's on-again-off-again boyfriend to the Big Apple.

9. "Force Seven"

CHiPs, 1982

In this season five finale of CHiPs (series love to tack backdoor pilots on a season finale) Ponch and Jon hardly appear at all, as they make way for Force Seven, an elite squad of martial arts masters who fight crime in L.A. The ninja cop crew features former NFL and future Hunter star Fred Dryer as the eye patch-wearing leader, as well as a ventriloquist with a Confucius puppet. Yeah, it's cheesy '80s action stuff, and we eat it up. John Rhys-Davies also appears, as does Tom Reilly, who would confusingly go on to play an entirely different character, "Hot Dog" Nelson, in the following CHiPs episode. It goes without saying that Force Seven never became a series of its own.

10. "The Coltons"

MacGyver, 1991

The family that hunts bounties together, stays together? An impressive cast of black actors — including Cuba Gooding Jr., Della Reese, Cleavon Little and Richard Lawson — portrayed the bounty-hunting Coltons, who each popped up here as minor characters in MacGyver. At last, in season seven, the entire gang came together for a spin-off pilot. Oh, and they had a cute bulldog named Frog.

11. "Retribution" …and many more

Diagnosis Murder, 1998

A spin-off of Jake and the Fatman, Diagnosis Murder constantly looked to return the favor. At the behest of executive producer Fred Silverman, each season offered up one or two nested pilots! Some of the notable examples are "Sister Michael Wants You" in season one, which starred Delta Burke as a crime-solving nun, and "Retribution" in season five, which featured Fred Dryer leading what would have been a new series called The Chief. Executive producer Lee Goldberg later revealed, "Nobody at CBS wanted to work with Fred Dryer." So they shopped it around. "Every [network] had some personal reason for not wanting to be in business with Dryer," Goldberg admitted. "And seemed to take great pleasure in passing on the project in the room to his implacable face." Ouch.