Grease
Grease is often remembered as the movie where Sandy changes everything about herself to win over Danny, mostly because that final black outfit does tend to dominate the conversation.

That is only half the story. Danny also tries to change for Sandy, briefly turning himself into a letterman-sweater-wearing nice boy before the carnival finale takes over. So yes, Sandy gets the more dramatic makeover, but Danny also spends part of the movie trying to cosplay as a respectable boyfriend.
