Many of Madeline L’Engle’s books are connected, even beyond the obvious titles that are part of a series. Suzy Austin is a perky kid sister in Meet the Austins (and sequels) for kids, and later shows up as a grown up Suzy Davidson in A Severed Wasp for adults. There are a few other L’Engle characters who do this as well, but as far as I know, none of them are the primary character in any of the books in which they appear.
Are you being sarcastic, or did you not get to the second paragraph in my first post? 
I have to admit, I’m guilty of that which I hate most: skimming the OP. Sorry 
Child characters from children’s books who grow up in adult books? OK.
Alice Pleasance Liddell Hargreaves. As a child, she was in Alice in Wonderland; as an adult, she appeared in Philip Jose Farmer’s Riverworld novels.
Mark Twain wrote a couple of sequels to Tom Sawyer with Tom getting older with each, but I’m not sure if he reached adulthood.
In movies, Hook shows a grown up Peter Pan.
The Dope is slipping. Time was an error like this would have been caught within a half-hour. Tsk.
I will be good-gosh-darned. I do believe I read that, without reading the rest of the series. Found it in the Library Quarter Books sale.
Robert Heinlein’s juvenile characters have shown up in his later books, as adults, I believe, during his later, weaker books. On the other hand, Hazel Stone appeared first as a grandmother, in a juvenile, then as a child, in an adult, then as an apparent 20-something in an adult.
PG Wodehouse introduced the character Psmith in his school story Mike, which was first published in a boys’ magazine. Psmith, best described as an eccentric character, proved more interesting than Mike (Mike Jackson, by the way), and later appeared in Psmith in the City, Psmith, Journalist and Leave it to Psmith, which were aimed at more adult readers.
Ender Wiggin, from Card’s books, might qualify. In my opinion, Ender’s Game could reasonably be considered a “young adult” book, while Speaker for the Dead is a more adult book.
Marvelmman was clearly for children in the 50s and adults in the 80s.
RealityChuck mentioned Farmer and Riverworld. I was also thinking of Dorothy Gale and other Oz personages in A Barnstormer in Oz.
A lot of childrens characters have neded up in porn films of one type or another. Us ually they are all grown up in the porn version (mainly to avoid critisism of being paedophilic).
Sleeping Beauty has many versions not suitable for children with a much more grown up main character.
Like Bambi in the sequel, “Bambi Goes Crazy Ape Bonkers with His Drill and Sex”?
I know that the adult book where she was a child is The Moon is a Harsh Mistress. Remind me what the other two are?
No, but Bambi did appear in Bambi Meets Godzilla, a grown up film.
I saw it, I just thought it was a Wonderland-NeverNeverland crossover.
The late Angela Carter made something of a specialty of short stories which re-told classic fairytales such as Cinderella and Bluebeard in decidedly adult fashion. She also wrote Alice in Prague, an adult short story which was a tribute to Czech animator Jan Svankmayer’s “grown-up” film Alice.
You got it backwards. Wicked is a prequel to Wizard of Oz.
Laura Ingalls is Laura Ingalls Wilder and becomes a mother in her last book.
The Rolling Stones (of course) and The Cat Who Walks Through Walls
Hmmm… the Murry family and Calvin are quite definitely protagonists in several books in which they grow up and age. Each seems to have center stage in a different book: Meg in A Wrinkle in Time, the youngest boy in the sequels, the twins Sandy and Denys (minor supporting characters in the Wrinkle series) being the protagonists in Many Waters, and then Calvin and Meg’s kids including Polyhymnia (whose problems with Poly vs Polly I strongly sympathize with! ;)) in yet another series of novels. The range appears to be from children’s novels to young adult, but that’s an artifact of Farrar’s marketing strategy; I don’t believe L’Engle herself ever intended to target specific audiences.
(sorry O.T.)
We shouldn’t dredge up Bambi Gasgcoigne’s unfortunate past problems, he was a child star who suffered the limelight too early and cannot be blamed for falling in with a bad crowd. He later made a succesfull return as a quiz show host, and that should be appluaded without all this muck raking popular within the gutter press.