It's certainly a funny and egregious error, though one easily remedied. But it reminded me of a far funnier and significantly more egregious problem by one of America's most successful playwright in the history of the Broadway theater. It was Neil Simon, and I heard him tell the story on himself.
Starting in 1983, Simon wrote the show Brighton Beach Memoirs, which eventually turned out to be the first of what later became known as the Eugene Trilogy, three semi-autobiographical plays. This first centered around teenaged Eugune Jerome's social awakening amid a loving, but occasionally-dysfunctional extended family (with his aunt and cousins moving in).
After that came Biloxi Blues, which dealt with Eugene's further growth as a young when he joins the army. And finally, three years after the initial play, Simon returned to the family in Broadway Bound, a story about Eugene and his older brother developing the first steps of their fledgling careers as writers and leaving home, amid a growing family turmoil, as the warm, cantankerous, socialist-loving grandfather does his best to be a voice of commentary and support.
There was one problem.
Between the time of writing Brighton Beach Memoirs and then another play and finally Broadway Bound three years later, Simon says that he was aghast to having totally forgotten that...he had killed off the grandfather in the first play!
And it's not a small matter. The very reason that the aunt and two cousins move in with the Jeromes is specifically because they'd been living with the grandfather, but he died. So, they were on their own, and therefore taken in.
(And it's all the funnier, too, when you remember that the three plays are semi-autobiographical!)
It's sort of amazing not just that he forgot about it, but funny too that it had the same producer (Emmanuel Azenberg) and same director (Gene Saks). And even the star, Jonathan Silverman, had been in the first play, Brighton Beach Memoirs -- not in the original cast, but as a replacement. So, a whole lot of the very same, major people were involved in both productions in their early stages, not to mention the same scenic designer and lighting designer.
I suspect that though all these other people did both shows, Simon likely realized the mistake earlier during the writing process. However he said that by the time he realized the problem, he felt it was too late to do anything, the grandfather was too important and wonderful a character, so he just accepted the gaff and moved on.