Yes, you can generally add someone to your Disney reservation in 2026, but the process varies depending on whether you are modifying a hotel stay or a dining reservation. For Disney Resort hotels, you can add a guest through the "My Disney Experience" app or website under "Modify Reservation," provided the room's maximum occupancy (usually 4 to 5 people) is not exceeded. Note that adding an adult may incur an "extra adult fee" per night. For dining reservations, it is much trickier; if you want to increase your party size from 4 to 5, the system may require you to find a completely new time slot because table configurations are strictly assigned. In 2026, Disney's AI-driven booking system is very precise, so if you cannot find a larger slot online, your best bet is to visit the podium at the restaurant 15 minutes early to see if they can accommodate the extra person.