For her split screen scenes, Lindsay Lohan wore an earpiece which would play back the dialogue of the other sister.
Actress Joanna Barnes played the "wicked girlfriend" in The Parent Trap (1961) and plays the mother of the wicked girlfriend in this version. In the 1998 version, the wicked girlfriend's name is Meredith, rather than Vicky. Joanna Barnes's character, as the mother, in this new Parent Trap is still named Vicki, however.
The lost boy who shows up at the girls' camp is played by Michael Lohan, Lindsay Lohan's real-life brother. Lindsay's siblings regularly appear as extras in her movies.
When Lindsay Lohan was 11 she pretended to be ill so she could skip school and go to her first movie audition for The Parent Trap (1998).