Contrary to some popular rumors, Lindsay Lohan never had a twin sister and used a double for some of The Parent Trap scenes. The New York native starred as both Halle and Anna in the 1998 remake of the film alongside Dennis Quaid and Natasha Richardson. To differentiate the characters, Anna had long hair, which she later cut, and spoke in a British accent. It is always fun to see a movie coming up with creative ways of portraying fictional twins or doubles, especially before CG faces and replacements were common.

https://screenrant.com/who-played-lindsay-lohan-double-parent-trap/