Disney took a children's novel from my beloved Erich Kästner called Das doppelte Lottchen, americanized it (which included making a single mom/Munich career journalist into a Boston socialite), called it The Parent Trap and now millions of people think that form is the original of the story.

Actually, Disney did it TWICE:

The Parent Trap (1961)

The Parent Trap (1998)

In the 1998 version, the twins' mother is a rich British designer of wedding gowns.

But I doubt if Disney is the only one who has altered the story on adapting it to film, as it looks like the novel has been adapted not twice, but SIXTEEN times--twice in the U.S., twice in Japan, five times in India, once in the U.K., once in Korea, once in Germany, once in Sweden, once in Lithuania and once in Iran. I guess everyone has had a crack at adapting this!

Oh, and I think I remember Erich Kästner from my own childhood. He wrote Emil and the Detectives, didn't he?