The news about Christie Brinkley reminds me of the changes in Season 8.
Originally, the season was advertised as the first U.S. season where a husband and wife would compete against each other: rodeo champion Ty Murray and singer-songwriter Jewel. The two had married the previous year after a ten-year courtship. However, just prior to the series, Jewel fractured both her tibias and was unable to perform. She was replaced on the show by Playboy model Holly Madison. Murray chose to continue on the show, and Jewel appeared during the season as a special musical guest.
Nancy O'Dell, the then co-host of Access Hollywood, was also originally announced to be on the show, but was forced to withdraw from the competition due to a torn meniscus, which required surgery. She was replaced by Melissa Rycroft, a former Dallas Cowboys cheerleader who won season 13 of The Bachelor. She only had two days to practice her first dance.