This collection of prospective pilots and continuations includes episodes where lesser-known characters were thrust into the spotlight, where side characters were given a shot at leading roles, and where main characters ventured out into unfamiliar settings. Regrettably, what unites these endeavors is that none of them evolved into full-fledged series.

The conclusion of “Laverne & Shirley” was notably absent of Shirley, due to Cindy Williams’ legal dispute with ABC, and featured scant appearances of Laverne, with Penny Marshall making a mere two appearances. Loyal fans who tuned in for the final episode were met with a backdoor pilot spotlighting Shirley’s former boyfriend, Carmine Ragusa, portrayed by Eddie Mekka. With Shirley married to army medic Walter Meeney and subsequently exiting the show, Carmine seeks new opportunities in “Here Today, Hair Tomorrow,” ultimately delivering one of sitcom history’s most disappointing finales.

“One Day at a Time” followed the Romanos—single mom Ann (Bonnie Franklin), her headstrong daughter Julie (Mackenzie Phillips), and the spirited Barbara (Valerie Bertinelli)—as they embarked on a new chapter in an apartment after Ann’s divorce. Although Barbara was the sole Romano featured in the series finale, the beloved building superintendent Schneider, portrayed by Pat Harrington Jr., was given an opportunity to headline his own show.

Deciding to really make a go of his acting career, Carmine uses his last dollar to get to Broadway and try out for a role in the chorus of “Hair.” At the audition, he meets smooth-talking Rick West (Ben Powers), who has been around the acting block. When Rick lands a one-room basement apartment, he invites Carmine to share the rent. Rick and Carmine are both cast in “Hair” in spite of their misgivings and seasons of hippie-dippy adventures are promised. But ABC wasn’t interested in this gender-flipped, ’60s dipped version of the girls’ dynamic and passed on the backdoor pilot.

“One Day at a Time” centered on the Romanos — the single working mom Ann (Bonnie Franklin), rebellious older daughter Julie (Mackenzie Phillips), and tomboyish Barbara (Valerie Bertinelli) — who move into an apartment building together to start a fresh life in the wake of Ann’s divorce. Only Barbara appears in the final episode of the series, but fan-favorite building super Schneider (Pat Harrington Jr.) got his own chance at a show.

In “Another Man’s Shoes,” Schneider learns that his nephew Keith (Corey Feldman) and niece Lori (Natalie Klinger) have been orphaned. He feels a responsibility to his brother’s kids, and thus decides to step in and take care of them. When he arrives to do so, the place where they’re living is in clear need of a new handyman and advice-slinger, so instead of uprooting the kids, he moves into their place of residence. CBS resisted the notion of Schneider grappling with single parenthood and the show was not picked up.

“The Equalizer” had a multipart finale. In one of its final episodes, “Sins of the Father,” it tried to spin off Elijah Reed (Titus Welliver) into his own series with his daughter Samantha (Juani Feliz) at his side. CBS was more interested in creating room on its schedule for spin-offs of “Fire Country” and “Blue Bloods,” so it decided not to pick up the Reeds’ antics to series.

“Sins of the Father” sees Robyn McCall (Queen Latifah) called into action when Samantha contacts her for help. Her father, Elijah, is in trouble, and Sam has no idea how or where to find him. Since her father is a former CIA agent who knows how to hide when the chips are down, this isn’t surprising. Roby and Sam investigate leads together and Sam learns more and more about her family’s long history. When father and daughter reunite, there’s a possibility they’ll become a crime-fighting duo for the ages — but fans will never get to see how that pans out.

“Green Acres” was part of one of primetime’s original multiverses: the Henningverse, created by executive producer Paul Henning, which encapsulated three separate shows which all contained characters who have roots in Hooterville. Ergo, when it was time for “Green Acres” to end, it’s not surprising the show tried to go out with a spin-off; the surprising part is it tried to go out with two. Sadly, both attempts were unfruitful despite absorbing the last two episodes of the show, robbing viewers of actual closure from the Douglass’. 

The first episode, “Hawaiian Honeymoon,” took Oliver (Eddie Albert) and Lisa (Eva Gabor) on vacation to Hawaii for a fifth honeymoon. Unfortunately for them, this is no sedate trip — the hotel they select has a wacky staff and they end up double-booked into the honeymoon suite. The second episode, “The Ex-Secretary,” focused on one of Oliver’s old employees, Carol Rush (Elaine Joyce), a scatterbrained secretary who lost Oliver’s watch years ago at the cleaners. Carol is now working in California as she juggles her job at a realtor with trying to reunite Oliver with his possession. Audiences never saw either set of characters again.

“The Facts of Life” had long drifted from its original premise when the show wrapped up during its ninth season, so it’s sort of quaint that the backdoor pilot that ended the show tried to take it back to its roots. It was once again about the girls’ boarding school alma mater, Eastland Academy, and the kids who matriculate there. “The Beginning of the End” and “The Beginning of the Beginning” sees spoiled Blair Warner (Lisa Whelchel) decide to step up and prevent Eastland from closing by buying it and becoming its headmistress. She finds the troupe of girls under her care are more difficult to guide than she anticipated. The pilot featured a young Juliette Lewis and Mayim Bialik as two members of Eastland’s next generation, showing plenty of unfulfilled promise.

“The Facts Of Life” tried to launch another spin-off that failed to develop during its third-to-final episode. In “Big Apple Blues,” Natalie Green (Mindy Cohn) moves to New York temporarily to follow her journalism career and ends up moving in with some quirky single types. Among the singletons is David Spade a few years before he found success in “Just Shoot Me.”

The last episode of “The Andy Griffith Show” is an interesting exception to the examples outlined above. While “Mayberry R.F.D.” actually did spring from the last episode of the legendary sitcom and ran for three seasons, its premise changed completely along the way. Only Sam Jones (Ken Berry) and his son Mike (Buddy Foster) are retained from the backdoor pilot; the episode’s other main characters disappear in the transition.

The episode “Mayberry R.F.D.” follows Sam’s attempt at moving to Mayberry alongside his Italian friend, Mario Vincente (Gabriele Tinti). Their plan to run a farm together is interrupted by Mario’s boy-mad sister Sophia (Letícia Román) and his grumpy Papa (Bruno Della Santina). The Vincentes are fish out of water in their new sleepy hometown, though the citizens there work hard to welcome them. Will they return to Italy or stick things out? Fans will unfortunately never find out. It might be one of the most rewatchable sitcoms of all time, but the pilot remains a confusing misstep that still puzzles viewers watching reruns decades later.