No Four Park Challenge right now… There is no Park Hopper allowed with the Disney Park Pass System. You also cannot book reservations for two different parks on the same day. For example, if you have a two day ticket, you can’t book it so that you’ll visit Disney’s Animal Kingdom in the morning and Epcot in the afternoon. I guess there’s a way around the system if you make two different My Disney Experience Accounts with different email addresses, but you would also need to use two different tickets for that. It would be expensive.