Hey Megan!
A very warm welcome and thanks for visiting planDisney with your question!
The Park Hopper option on a multi-day Disneyland Resort
Theme Park Ticket applies to all days on the ticket. There is no option to add the Park Hopper option on only a single day. But, you may purchase a 2-Day One Park Per Day Ticket and a 1-Day Park Hopper Ticket. During the reservation process, you will be asked to select your desired theme park for each day of your visit.
On your Park Hopper day, you will have the option to hop to the other theme park starting at 11:00 a.m. You will not be required to make another
Theme Park Reservation in order to visit the other park. And, you may hop back and forth as often as you like (subject to attendance availability.)
Have a wonderful time at “The Happiest Place on Earth!” Head on back to planDisney with more questions!
Tiffanie