"Tonight" host Jay Leno asked the 24-year-old about touchy subjects including her court appearance and brief jailing Friday, her family and what she's learned from her experiences.
The person spoke on condition of anonymity because NBC had announced Lohan's appearance but not its details.
Lohan's appearance was taped separately at the conclusion of Monday's show. The "Mean Girls" star is a late addition to Tuesday's lineup, knocking a scheduled guest, Broadway star Kristin Chenoweth, to another date.