According to the commentary, Naveen took some time to find the perfect voice actor. After reaching three possible candidates, they brought in their female staff to listen to each actor. Bruno Campos had the biggest "swoon" factor.
Flynn Rider from Tangled was designed when the directors gathered up every female animating for Disney, tacked pictures of celebrities and princes to the wall, had them analyze which specific features were the most attractive, and created Flynn from that. It was called, I kid you not, "The Hot Man Meeting".
Prince Hans in Frozen, Anna even engages in some non-sexual Eating the Eye Candy with him. Actually an example of Evil Is Sexy. Kristoff is also designed to be rather appealing, particularly more evident when compared to the more child-like earlier designs.