This might be an unpopular opinion, as I don't really see anyone talk about this. But I recently saw Wicked on Broadway again with a friend who had never seen the musical or movie. She loved it so much that she wanted to watch the movie the next day which we did. Her favorite character in the musical was Fiyero but she was disappointed that the Fiyero in the movie is completely different, which I didn't realize before.

Basically, the movie completely cuts out the "frat boy" aspect of Fiyero's character. Think about the difference in their first scenes:

In the musical, he's asleep being ridden around in a carriage. He says "I'm sure I won't last longer at this school than at any of the others" and doesn't care at all that the carriage hit Elphaba, and just makes the offhand comment "maybe the driver saw green and thought it meant go."

In comparison, Movie Fiyero is much more dashing from the very first scene. He arrives on horseback (much more independent and strong than being taken asleep in a carriage) and is immediately fascinated by Elphaba.

Movie Fiyero does still teach the students how to have fun but he never really has that shallow "idgaf about anything" attitude. We're told in dancing through life that he's like this, but we never really see it. Correct me if I'm wrong, but the movie doesn't even mention that he has a scandalous reputation and was kicked out of his previous schools.

To put it simply, Fiyero in the musical develops into the dashing, heroic character that he is by the end whereas movie Fiyero starts out that way. Fiyero's arc is supposed to be that he grows through with his relationship with Elphaba. He becomes fascinated with her slowly, rather than right away from the beginning. He goes from lazy and shallow to brave and righteous, finding Elphaba and standing by her side.

The movie has cut all of that short by having him start out that way. IMO, Fiyero's development/character arc won't hit the same in Part II as a result.