As, indeed, did K-9, eventually.
Paul Williams as a program about a kiddie show host named Marvin the Martian .
Stormbreaker aka Alex Rider: Stormbreaker was meant to be the first installment in a franchise based on the Alex Rider YA novel series (basically James Bond, Jr.). It was a box office bomb, and the franchise died on the vine.
There is now, however, a streaming series based on the novels, on the IMDbTV channel (which is somehow a thing that exists - it’s a streaming channel on Amazon Prime run by the Internet Movie Database website).
When the triplets were born, they were already testing the waters for some kind of sequel, or continuation, or whatever, when Fred MacMurray eventually refused to do the show anymore, and Ernie was too old to be a kid, because the last line of the episode on which the triplets are born, is Robbie saying something about his wife “and my three sons.”
Kinda like on Mom, currently, when it was pretty obvious that either Anna Faris, Allison Janney, or both were mumbling about leaving, when Kristen Johnston joined the cast and her character moved in with Marjorie-- the two are now poised to become a surrogate mother & daughter so there’s still a “Mom” relationship. They even brought in Marjorie’s estranged son in for a reconciliation. And Jill has been trying to have a baby for seasons; now she has a very serious boyfriend.
I’m predicting that now that Faris is gone, Janney will either leave as well, or fade to the background, but everyone else will either be a mom or a daughter in some way.
Originally there was supposed to be a fourth installment of “The Mummy” series with Brendan Fraser. It is certainly set up at the end of
“The Mummy: Tomb of the Dragon Emperor” where Jonathan leaves for Peru “where there are no mummies” only with a on screen note that the following year mummies were discovered in Peru. But the next installment “The Mummy:Rise of the Aztec” was never filmed.
To elaborate on the Die Another Day example, apparently they got so far as to write the script and cast the film before the plug was pulled due to the truely horrible critical reception to the film, they were fully expecting fans to love the movie so much they’d buy into Halle Berry’s NSA Spy. It also explains why Michael Madsen has so much screen time as Halle Berry’s boss for such a nothing roll. In addition they were planning on two more Bond films with Pierce Brosnan before that film also torpedoed his own Bond career.