Yes, you can add the Park Hopper option to your Disney World or Disneyland tickets in 2026 after they have been purchased, provided the tickets have not yet expired and still have remaining days on them. This is typically done through the My Disney Experience or Disneyland App by selecting "Change Ticket," or by visiting a Guest Relations window at the entrance of any theme park. However, there is an important caveat: you cannot add the Park Hopper for just "one day" of a multi-day ticket. Disney requires the add-on to be applied to the entire duration of the ticket. For example, if you have a 5-day base ticket and decide on day 3 that you want to hop, you will still have to pay the flat fee for all 5 days. Because the price of the Park Hopper add-on is fixed regardless of when you add it, it is usually more cost-effective to decide early in your trip. In 2026, with the removal of "all-day" hopping restrictions, you can move between parks at any time of day, making the add-on more flexible and valuable than it was in previous years.