As for Will & Kate, Their Takeout Food of Choice is...
Curry. Kate confided this to BBC Radio One in 2017, and while Will seemed to agree, he noted that he can't really handle spicy food. They also clarified that the food doesn't get sent to Buckingham palace but rather gets picked up (by someone other than themselves obviously). Indulging in a tasty takeout curry while watching box-set television sounds pretty normal to us!