Potential first episodes of TV shows are called “pilots.” Sometimes a TV show will try to launch a spinoff via a “backdoor pilot”—a sample of a new series that airs as an episode of the mother show. Successful backdoor pilots: NCIS from JAG, and Private Practice from Grey’s Anatomy. Unsuccessful ones? These.

Tales from Springfield

One of the most popular episodes of The Simpsons broke the form of a typical episode. Instead of one or two main stories based around the Simpson family, “22 Short Films About Springfield” told, well, 22 short stories about various residents of Springfield. (For example, Principal Skinner has Superintendent Chalmers over for a disastrous lunch, and Moe gets robbed immediately after Barney pays down his enormous bar tab.) The episode almost led to a Simpsons with less Simpsons, a show comprised of sketches called Tales from Springfield. The Simpsons writing staff pulled the plug once they realized they couldn’t produce two shows at the same time.

The Daleks

When the BBC’s long-running Doctor Who launched in the mid-1960s, the breakout characters were the bad guys—the Daleks, an army of angry, robot-like aliens. Who writer Terry Nation, who created the characters, wrote a pilot for a Dalek-based show in which they went to war with the “Space Security Service.” It aired in 1965 under the title “Mission to the Unknown.” Nation’s bosses at the BBC decided that less was more with the Daleks, choosing instead to have the show use the characters sparingly. His pilot was rejected, but it was made into an audio play in 2010.

Witchright Hall

A series about the goings-on at a special boarding school for young people with magical abilities? Sounds like a can’t-miss smash hit…except that we’re not talking a Harry Potter TV show. In 2001, the sitcom adaptation of the comic book Sabrina the Teenage Witch introduced a wayward teen witch, cousin to Sabrina, who gets shipped off to Witchright Hall, a reform school for the bad and magical. Network WB declined to turn the episode into a series…and canceled Sabrina not too long after to boot.

Cavender is Coming

There aren’t too many funny episodes of The Twilight Zone. Actually, this is about the only one—it even has a laugh track. This 1962 episode of Rod Serling’s spooky anthology series was a potential comedy about a wings-seeking angel named Cavender tasked with helping humans improve their lives. His first assignment: a woman named Agnes Grep, a klutz with a messy life played by a young Carol Burnett.

Sister Michael Wants You

In the 1990s, the crime procedural Diagnosis Murder, about a doctor that solved crimes, marked Dick Van Dyke’s return to television. Executive producer and former network boss Fred Silverman asked writers to create at least one (failed) backdoor pilot every year. Some of those included a cop show called The Chief starring ex-Hunter star Fred Dryer. The most interesting would have to be the episode titled “Sister Michael Wants You” in 1993, a set-up for a light-hearted action series in which Delta Burke of Designing Women portrayed a crime-fighting nun.